hydroton and PH

orgmacdonaldOctober 1, 2010

I'm using some hydroton in a flood/drain that's been sitting in the closet for a few years. I washed,rinsed, and let it soak in ph 5 overnight. Last time it was in use I remember having no ph problems at all. Now, I'm going from tap H2O at 8, adjusted to 5, and back up to 8 overnight. First, I blamed the tap water but after mixing up gallon and letting it sit out overnight I'm back to blaming the hydroton. I left half sit in a small bowl and the other half in a larger bowl filled with hydroton. The water only half is steady at 6, but the hydroton mix is up over 7. I'm leaning towards bacteria/fungus even though there aren't any visible signs. Any other ideas? I've read a lot about washing/sterilizing but don't really know where to go. H2O2 or bleach? What ratio? Bake in the oven or microwave? Has anyone overcome a similar situation?

I'm testing ph with liquid, i've lost faith in my meter. Although the plants don't mind (just harvested a great crop of romas and chiles), I'm losing sleep not being able to get a handle on this.

thanks in advance for your help.

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I would advice you to simply boil your hydroton for about half an hour (that should kill any pathogens without leaving any chemical residue) then leave it in a vinegar solution (1 part vinegar 2 parts water) for at least 2 days. Then rinse with water until all the vinegar is gone and use. Probably while your hydroton was stored its basic surface sites were activated and it is now self-buffering your nutrient solution through cation exchange. I would NOT think this was fungus or bacteria as these tend to lower instead of increase pH. Let me know if it works :o)

Best Regards,


Here is a link that might be useful: Visit my blog at science in hydroponics :o)

    Bookmark   October 1, 2010 at 1:17PM
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Thanks Daniel. I will give it a shot and post the results.

    Bookmark   October 1, 2010 at 1:46PM
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Hi orgmacdonald,

Is it right that Hydrotron® recomends soaking their pellets in PH 5 water for 24 hours and that this will stabilize the PH?

I was suspecting cation exchange at work as well, as clay does the main cation exchange in nature anyway. But was confused about the rather drastic increase in pH, while it would be more likely to stabilize at around maximal 7, with hydroton having a rather neutral buffer without any conditioning. Also cation absorption is more likely to happen in a short time as any release. Anyway, are you sure it''s going up to 8 and not to 7? As you have rinsed it, there are no dusty clay particles left, that would accelerate any effect either, right?

I don't see how hydroton would change it's chemical properties when stored for a longer period. From the guts I'd exclude bacterial or microbial influence as well, just because there's nothing of use for any microorganism in inert material as hydroton. It's truly not likely to hold any "life", especially if kept dry. Besides, any bacterial or fungal influence would take much longer than "overnight" to become active or activated. There is one more possibility: what if the hydroton just plays the role of a physically active, but chemically rather neutral catalyst and simply accelerates physical bicarbonate absorption from the atmosphere?

Reading your description again, I realize that you have got the PH rise effect with pH corrected tap water. But what about using your hydroton (simply rinsed and conditioned as recommended) with a specific nutrient solution? Also, depending on formula (product), you may have various nutrient pH buffers coming to action, which "normally" overrule the hydrotons buffering tendencies and influence(s) - at least over time. In other words, are you using the same nutrients than you did before?

Besides Daniel's recommendations, I guess it's important to know what the pH would be- and where it would move over time, when running a specific (most importantly your) nutrient solution, and even various alternative formulations and concentrations.

Nothing wrong with cooking hydroton and conditioning it with a vinegar solution, - I am just wondering what people with a few hundred liters of hydroton to process might do instead... ;-)
Maybe just hoping that it's circumstantial and/or a temporary effect only. And that the prolonged exposure to well buffered nutrient solution-, respectively using a more strongly (chemically) buffered nutrient solution would just do the trick...


    Bookmark   October 1, 2010 at 11:32PM
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Hi Lucas,

I think you are underestimating the capacity of cation exchange to change pH. Clays - especially those that have been dry for long periods of time - tend to be very basic and they will buffer a solution (especially if its poorly buffered) from 6.8 to even 9 in overnight. Also clays do increase their basic activity if they are stored for prolonged periods of time due the oxidative activity of atmospheric oxygen that creates basic defects within the crystal structure. Of course, this depends on the actual nature and composition of the clay but it does happen with certain frequency.

In commercial operations where media needs to be buffered the easiest thing to do is to first run a pH 3-4.5 buffer over the media within the hydroponic setup for a few days, adding more buffering agent if the pH drifts. When the pH remains constant the solution is ready. Usually good these buffering agents include acetate/actic acid and phosphoric acid/hydrogen phosphate but others such as citric acid species may also be used. Especially since they also have the ability to chelate cations and make the process faster. The initial buffer is usually prepared at 0.5 mM but the concentration can be increased if needed. After this the system is flushed and the crop is started.


    Bookmark   October 2, 2010 at 7:16AM
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Did I underestimate cation exchange capacity of clays here - and what makes you think so?
We are talking about HYDROTON respectively similar products, aren't we? I mean we deal with a highly fired and expanded clay that has become (almost) inert and has not even remotely the same chemical properties nor capacities as non-fired or ordinary and various clays as we find them as pure deposits or as soil components in nature. Although Hydroton is technically speaking only "biscuit" and not a fully vitrified clay, -you can't compare it's properties to any non-fired clay. Also, especially with a product like hydroton, we don't deal with an average or random clay composition, but with a distinct kind of clay, that was chosen and composed (most probably mixed) for it's "minerally neutral" properties.

Also, in this case (with a fully inert matter) dry is dry, there is no physical nor chemical difference possible in the degree of dryness. Compared to non-fired clay, it is truly inert and can't dry out any further, not even in a thousand years. Happens that I am a former potter, who studied this trade at the Arts Deco Ceramic academy in Geneva (Switzerland) and was practicing ceramic and pottery applications for over 20 years. ;-)

Nevertheless, remember that hydroton has formerly been developed and introduced as a "hydroponic media for dummies". It serves it's purpose since decades for people who have no or no extended knowledge of pH conditioning and who most probably will not even come across terms like cation- or anion exchange in their lifetime!

You didn't comment on any other of my comments, recommendations and suspicions, - how comes?
Does abstention in this context mean affirmation - or is it more like intended to avoid any affirmation?

You could at least comment or give your opinion on my suspicion that what ever caused the pH raise wouldn't necessarily happen with a decently buffered nutrient solution? Instead you say that the pH raise could even be more severe with "poorly buffered" solutions, and imply that I am underestimating the capacity of cation exchange to change pH. Hey, that's why I recommend "repeating the experiment" with a nutrient solution at full concentration and with decently buffered pH. ;-)


    Bookmark   October 2, 2010 at 11:43PM
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"Happens that I am a former potter, who studied this trade at the Arts Deco Ceramic academy in Geneva (Switzerland) and was practicing ceramic and pottery applications for over 20 years. ;-)"

I'm a former potter myself, not 20 years (I'm not that old) but 4 years for me. The only difference between fired (even low fired, bisked fired), and non fired clay that I can see is dead bacteria in the fired clay (and of coarse it fuses together). But I'm not a chemist, and nobody in our class was. I hardly think that's the focus of any ceramics class. But I also know the difference between the surface area of a hydroton rock and a piece of pottery is significantly diffident.

    Bookmark   October 3, 2010 at 6:37AM
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Hi Lucas,

You are indeed underestimating the cation exchange capacity of clays. Hydro ton is a clay, fired and expanded but a clay. Its chemical composition does not include any water within the crystal structure and it has larger pore size but it is still a clay. Expanded clays like hydro ton which have been fired at high temperatures do preserve a significant degree of cation exchange capacity which can increase with dry storage. Atmospheric oxygen does react with such clay structures when they are dry (easier with expanded clays) and increases their exchange capacity due to the creation of basic defects. I know this to be true (from cation exchange capacity measurements and basic site quantification of such clays) so feel free to run experiments and verify it.

Regarding my lack of comment it is merely because you tend to get into pretty heated debates easily over such issues so I feel no need to comment and start such a discussion this is why I prefer to keep my comments to your posts at a minimum. I don't mean this to be offensive just that personally I'd rather not spend my time in such debates.

I just wanted to write a reply to help a person with a hydroton issue using the knowledge I have acquired as a chemist and I think I have finished my task so I will not continue commenting on this thread :o)

Best Regards,


    Bookmark   October 3, 2010 at 7:15AM
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take the hydrotron out of the picture, how strong are the buffers in the water. it is not unusual for water buffers to repeatedly bounce back and fourth some never stabilizing. in the aquaculture industry it is a nightmare. particularly if the municipality changes or mixes the source of water that is why R/O water comes into play. have you used deionized water to see if that may be the problem?

    Bookmark   October 3, 2010 at 10:21AM
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I think (besides the theoretical disagreement) that this is a circumstantial case and problem - and can't be solved with theoretical knowledge (alone). It is actually very simple: if the directions of the manufacturer are followed and the Hydroton has been conditioned properly and yet you have extreme pH swings, the problem is very likely to not be linked to the Hydroton but 'water quality born'. It's actually a classic.

Besides, my intention is also to merely help and to find a solution to the current problem. But to do so, the real issue(s) have to be found. And if necessary sometimes debated for the sake of clarity. Sorry, but that's the usual course and deal in forums and sometimes truly advantageous.

My suggestions are unchanged. If following manufacturer's instructions and the result still ends up in extreme pH swings, control water quality and repeat the experiment with full strength nutrients. Optional: switch to different nutrients, increase concentration somewhat, or change/modify buffer capacity (switch to brand with better pH buffer) if required. In case you plan to run a week nutrient concentration, the buffer capacity of the solution is obviously weaker - and water quality matters even more. If using a rather strong nutrient concentration (maturing tomatoes for example) base water quality is less important as the chemical signature of the solution is modified even more (hopefully towards pH stability) with increasing nutrient strength.

PS: the most significant difference between high fired, expanded clay pebbles and 'natural and unfired clay' is obviously that unfired clay would dissolve to a smeary puree in minutes and is hence unsuited for any hydroponic applications. Compared to naturally occurring and unfired clay, expanded clay pebbles are chemically inert and pH neutral. Not only in my opinion, but according to several sources (notably General Hydroponics) I was consulting to back up what I was anticipating. Water retention capabilities vary largely by type and brand name, in fact according to composition and firing temperatures (ranging from 900 to 1200 degree C). In this very context, clay is truly not clay and both kinds can't be compared as suggested.

Also, several studies have shown that various clay pebbles produce inconsistent results from product to product. As for the "overnight" effect: A study showed, that Aggregate interior pores can take months to become fully saturated under normal saturation procedures (Holm et al., 2004). A typical product, as HydRocks (Big River Industries Alpharetta, GA) for example has no significant nutritive value and a LOW cation exchange capacity (5.12 meq/100ml only).

- "Expanded clay has been classified as an inert material with no cation exchange or buffer capacity."
Source: Soilless culture: theory and practice By Michael Raviv, Johann Heinrich Lieth -

Other sources say that expanded clay has been successfully used to increase water holding and to "substrate" cation exchange capacity. I couldn't find any source that mentioned any high and/or short term pH swings, due to the expanded clay's CEC.

I guess I haven't been underestimating the CEC of expanded clay but was estimating and rating it accurately when clearly differentiating it from clay - as well as concerning a general context as in this specific case.



    Bookmark   October 3, 2010 at 11:28PM
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I thought the water thing was ruled out on the original post, when Orgmacdonald did the Ph adjusted water with and without Hydroton overnight diagnostic test thing.
Or did I miss something?

    Bookmark   October 4, 2010 at 12:31AM
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Thanks for all of the replies and suggestions. I am using the same nutrients as before - pure blend pro. Good or bad, I'm not sure but I have had some pretty good luck in the past. My concentration is low, so I guess my buffer is weak but I still think there are other issues. I will repeat the experiment and with water from the tap and the store using both low and high nutrient concentrations.

    Bookmark   October 4, 2010 at 8:21AM
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I am having much the same issue in my ebb/flow table filled with hydroton. I never soaked the balls in low PH water overnight and perhaps this is the issue. My water PH jumped from 6.1 to 7.4 in an 8 hour period. What is strange is that I added more water to the reservoir and ph'd it to 6.1 about 3 hours ago...and my lights are off and therefore the water is just sitting in the rex. I went down there about 3 hours after adjusting to 6.1 and now the water is 6.5!!??

I calibrated my meter several times throughout the process. Any thoughts?


    Bookmark   October 6, 2010 at 4:23PM
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My thoughts are something, possibly calcium, in your source water.

    Bookmark   October 6, 2010 at 4:37PM
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So, I put 12 gals of ph adjusted H2O in my system and let it circulate constantly for 2 days with little or no ph change. I'm testing with drops so it's hard to say what, if any change occurred. Yesterday, I added a couple of liters of hydroton in the morning and by the time i got home from work ph was definitely over 7. I started at ~4.
Now what? I haven't soaked anything in vinegar yet but have been trying to keep the solution around 4 to try and reverse whatever is going on. Should I just soak it in vinegar and get it over with or is there something else i can do?

Thanks for all of the responses. Please keep them coming.

    Bookmark   October 7, 2010 at 6:07AM
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My earlier assumption, that the Hydroton would merely play a role as a physical (not actually chemical) catalyst, was in fact based on a similar case where a huge amount of rice hulls was used as medium. Same thing happened: while pH corrected water kept a rather stable pH, - once it ran through the rice hulls, pH moved drastically upwards overnight. Even after being corrected once again.

Actually rinsed (or parboiled) rice hulls aren't supposed to raise pH either in such short time (certainly not chemically). Well, truth to be told, the not very scientific but practical solution (not mine, though) in this case was to replace the rice hulls with a synthetic agro-foam that didn't absorb any of the water. Problem not actually understood and yet solved ;-)

The other point is that it looks like you haven't added any nutrient (decently buffered or not) and actually not repeated the experiment as suggested - or have you? Using an actual nutrient solution with a well buffered formula (at a decent strength, because the higher the EC the better the buffer will be) would most probably show very different results, respectively may stabilize the pH. Also, you haven't ever specified what you did actually use to get the pH, down to 4. There might be a clue in this "little" detail.

Last but not least, - however and whatever happens, and what the actual role of the Hydroton finally might be, if there is a tap water (or pH down) related problem it has to be solved seperately and regardless of the media. Btw: tap water quality and signature are prone to changes (either because of the add of new "sources or wells" to the water supply net or with seasons). To stick the problem to the Hydroton and rule the "water thing" out for sure as a reverse logic, - one would have to change the media (different expanded clay, gravel, lava rocks, etc) with similar (or quite similar) physical properties and test if the pH wouldn't do the very same thing, respectively would keep stable with the change instead.

    Bookmark   October 7, 2010 at 8:20AM
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Lucas, thanks for the response.
No, I didn't repeat the experiment and it may be short sighted but I am blaming the hydroton for my ph drift. I'm using Earth Juice ph down to adjust the ph. You are correct in that I am not using any nutrients for the time being but based on experience, I'm sure the buffer will have no affect on the results.

    Bookmark   October 7, 2010 at 12:00PM
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The cause of your pH drift is most likely the hydroton. Adjusting the pH every time it drifts is not going to be a very effective solution since basic sites can be abundant and it can be weeks or months before you neutralize them this way. As I advised before, simply soak them in vinegar as I explained and your problem will most likely get solved. I have always treated clays (expanded or not) in this way and the pH drifting problems have always been fixed.

    Bookmark   October 7, 2010 at 1:29PM
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No offense intended, but you haven't considered nor applied any of the recommendations given so far from both sides... If you simply repeat what you have done earlier and which definitely hasn't worked, you can't expect any improvement, can you?!

I wouldn't blame the Hydroton, firstly because it is not only chemically neutral, but also if applied mutatis mutandis. In other words, the Hydroton is just a thing, can't do anything wrong and hence can't be blamed. ;-)
Have you made some research about the stability of "Earth Juice ph down", being a "natural and organic" pH down? Looks like there are indeed a number of reports of stability issues with this product, which are even called a PITA by some. Have you considered this product (actually this choice) being the cause at the end?

I haven't vetoed the "vinegar solution" proposed firstly and confirmed again working by Daniel, and yet I don't see how it could be different from any other acidic conditioning - actually and initially recommended by the manufacturer. Except of course that it would most probably beat any unsuited pH-down for the purpose (as Earth Juice?) head and shoulders - LOL!
At least try this-one!

Or, last but not least, has it ever crossed your mind to call Hydroton (brand name right?) and report your problem to them - and as you caught them off guard, simply asking for a suited, recommended and approved pH conditioner?

    Bookmark   October 7, 2010 at 11:06PM
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I personally have never had a pH problem using hydroton, but I have not let it sit for years between uses either. But I'm sure that some sit in a whorehouse or store and such before it actually gets used. Bottom line I haven't had that problem so I don't really have any suggestions on it. But when I clean the hydroton between uses, I use white vinegar (about 1/3 vinegar 2/3 water) to clean the salts off of it. It just needs to be rinsed many times to get the smell out, but works quite well.

Also I wanted to say that even though Earth Juice pH adjusters are considered organic, they work just fine. I was warned by General hydroponics about Earth Juice's organic adjusters not being stable, they were just wanting me to use there product. But fact is I have never used anything other than Earth Juice dry crystals.

I bought 1 pound of each (up/down) well over a year and half ago and have not even used it up yet. That's after 6 or 7 different hydroponic systems (3 using hydroton) with reservoirs from 15 to 50 gallons, and changing the nutrient solution from every week to every 3 weeks. From my experience Earth Juice pH adjusters are quite stable, and the only way to go. Simply because a little goes a long way, not to mention that dry crystals are much cheaper to ship than a liquid (the reason I got them in the first place). If they were unstable I simply would have used them up a long time ago if I had to readjust pH all the time.

    Bookmark   October 8, 2010 at 2:42AM
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It simply depends on water quality. In some case (with a specific and "ideal" water signature) in combination with buffered nutrients you don't need any pH-down (or up) at all. Perhaps a pinch of citric acid. You can in fact (with clean tap water) easily adopt your nutrients in such way that they are stable enough by themselves. With highly alkaline water and unbuffered nutrients, only the strong stuff, like Nitric Acid or Sulphuric Acid would work - and any "organic Ph-down" would simply not be up to the task, unless you repeat the procedure over and over again ad noseam. Independently on media, including expanded clay, of course.

Btw: stability of any product and the needed- or used-up amount over time aren't necessarily correlated. If your pH only needs little corrections (hence very small amounts of pH up/down), because the used water plus formula and buffer of your nutrients "mainly" do the trick, - you obviously use up very little of any pH down/up. And nearly any product or suited chemical would work and be good enough. If on top of that you do frequent nutrient changes, you "use-up" even less :-)

Anecdotical evidence combined with a selective observation: If some product (like Earth Juice pH adjuster) is stable under one specific condition (a personal experience) , and suited for one case, - this doesn't mean that it is actually stable or suited for various other conditions. Unfortunately, it doesn't exactly say if it is suited for a recommended standard conditioning of expanded clay either.

    Bookmark   October 8, 2010 at 5:58AM
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PS: at homehydro, watch that "correct while your type" feature of your automatic error correction, because that's most probably how the "whorehouse", or expressions like "of coarse" or the "clams" that you sometimes claim, as a few other odd orthographic disfigurements probably find their way into your text. ;-)

I actually have no problem with it, as it's rather funny - but as it is a bit too frequent - I thought I'll give you a hint. Didn't you originally say that people may not get aware of some interferences (your analogy with bad breath) , if anyone states the discrepancies!? ;-)

    Bookmark   October 8, 2010 at 6:46AM
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Suggestions? So far there has been one decent suggestion from Daniel and one big pissing contest. I originally posted here because I was hoping for an answer not another flaming session.
So, here's an update. Like I said before it IS NOT the water. There are only so many hours in a day and I can't possibly do everything at once, so first I ruled out the water by running just water, no nutes, no hydroton, no plants in my system, just water. PH was steady for days. Hours after adding hydroton the ph went up significantly. I'm no scientist, but I'd say it's the hydroton. As previously mentioned, I've ran the same nutes/ph down in the past w/o issue. So, can we stop beating around the bush by blaming the water,ph down,nutes,and the kitchen sink?
To hopefully correct the issue, with Daniel's advice (thank you Daniel), I soaked and washed the pump and trays with Physan 20 (disinfectant, fungicide, virucide, and algaecide), rerinsed the hydroton, and am currently soaking it in a 2:1 water, vinegar solution. On Sunday, I'll rerinse, put everything back together, cross my fingers and hope for the best.
I've picked up a lot of info here, so thanks for all of the responses but I really don't think it's very useful getting into personal attacks or posting to deliberately irritate someone. It drives people away and it does nothing to collectively resolve an issue.


    Bookmark   October 8, 2010 at 7:54AM
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I hope you didn't think me reply about calcium in the water was a suggestion that water was the culprit. I was replying to brian's post. Sorry if I caused confusion.
Please let us know how it turns out after soaking the hydroton. I tend to agree with Daniels assessment. the hydroton istself is not the issues so much as the amount of surface area available to hold things on it.
And yes the arguing is petty and annoying. Unfortunately, this forum is unmoderated so we have no choice but to hear it.

    Bookmark   October 8, 2010 at 2:46PM
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Personally I was just trying to give some insite on Earth Juice pH adjusters from my first hand knowledge and experience from using them. Like I said "From my experience Earth Juice pH adjusters are quite stable." Assuming that water quality is a factor in it's stability, you can hardly blame Earth Juice for water quality. That would be a water quality issue, not the pH adjuster. And I am not assuming that orgmacdonald has water quality issues.

Thank you, but I'm very much aware that my spelling is quite substandard. I have been dealing with that issue for as long as I can remember. I do spend a lot of time trying to get spelling right and spell checkers don't help much. They only put a red line under a misspelled word, they don't check definitions and if the word is used in the right context. I do open a another browser window and check definitions for many words in order to check that aspect, but I can't possibility do that for every word. Top that off with the fact I have Dyslexia that was not diagnosed until I was out of school, so I never got the right instruction/training to deal with it. That makes trying to communicate correctly with written words difficult for me at best. But that's not going to keep me from trying.

    Bookmark   October 8, 2010 at 9:43PM
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Orgmacdonald, from what I have read on here in the past, Daniel is top notch. He seems to be not only intelligent, but very helpful. Doesn't seem to try to use forums as means to reinforce his ego. I'm really interested in hearing of your results.

    Bookmark   October 9, 2010 at 11:41PM
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What's up with you - where's your self-esteem compadres? Keep your powder dry and don't pee your pants before the contest has even started! Seriously - why justifying so vehemently, all of a sudden, - just because someone said the "P-word"?

A "pissing contest", really? Don't you dare LOL! Although I keep sanguinary language for extreme cases - I guess if you drop anyone from a tree and let them roll down the hill, you can always call them walnuts as well. Or starve someone for 3 days, put them up in a banana tree and call them a monkey as soon as they start scarfing unripe bananas down with the peel? If then the guy (or the gal) still justifies for it eventually, you got them real good! ;-)

Just because there was a bit more going on than just quick and accurate problem solving (in fact) to an actually paradoxical problem? More textbook smart-alecing and wannabe expert competition as expected? Medium personal animosities - of the kind they are actually standard procedure in almost any forum now? Honestly, I have probably seen it all in almost 15 years of forum activity - and I truly have seen WAY worse that wasn't ever called that way.

Oh, I see... some guys simply justify themselves and hope for the illusion of the reverse prima facie presumption? How smart is that!? LOL

You want a pissing contest, then down with your pants and stop that double dealing!

The unadorned truth is that you are looking at a "severe dyslexia survivor" who started suffering from it at a time when it was in fact nearly unknown and not even considered by teachers. It's hell and you may (speaking of which) loose your self-esteem until much later you and others know better. Every case is different I guess, but over 40 years later I am fluent in 4 languages (spoken and written), while English is actually my 4th in order of appearance and skill-wise. I even have working knowledge in a few others today. Almost "cured" myself I guess - but only almost, as I have to admit that I still need to check and recheck my spelling to be certain of not having committed and missed more than average "odd" spelling mistakes.
And no - you don't need to kiss anyone's ass, not even the ones of all others involved and/or only watching - to explain the fact away that you might be part of any "wee-wee contest" at the gardenweb forum. Don't zip-up your fly yet - you may have made it to the semi-finals after all! LOL

Aren't you one backstabber of a kind? Do you really need to subtly play people's qualifications against each other? Daniel has proven to be very accurate when it comes to chemistry and related topics (that are often backed up with scientific facts he knows of or directly refers to), - but that makes it look even more odd, when he seems to not be exactly scientific but rather anecdotical about the details in this case. Double standard apparently applies if anyone else comes up with some scientific facts and back up- or what? How funny is that?! Looks if you are perfectly eligible for the contest as well. You may proceed to enqueue asap. ;-)

@orgmacdonald: As for me, I don't need to be invited to stay for diner by you nor anyone else - but hey, watch your tongue with others. Same as Joe, you like playing people against each others in such terms of endearment? With such double dealer mind games you better don't leave the comfort zone of a forum. You better stay out of the reach of really mean and actually pissed people. I've seen a couple of backstabbers getting a bloody nose, or even shot in their face for less. Then again, here is not much more at stake than getting a even more pious opinion in exchange for your own. You, as the initiator of the pissing contest have the honor of starting as soon as you are ready ;-)

In General:
This topic has started with a fine paradox in the first place and even if the vinegar works (as good as any suited conditioner for expanded clay should) it is just standard procedure recommended by the manufacturer. In fact the very and sole thing the topic starter did either miss or didn't do with the appropriate product. And yet, we still haven't learned why the expanded clay- water and pH-Down combination behaves differently in this case. And at the end we haven't probably learned either if the Earth Juice pH down was/is an appropriate conditioner for Hydroton and/or for any other expanded clay pebbles - or not. Furthermore, we will probably never know if there was something wrong with the Hydroton, and if yes - what it was?!

You might say "who cares"? Well as I start to be truly pissed, I actually don't care any longer either. ;-)

    Bookmark   October 11, 2010 at 4:14AM
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You are the only one who cares what languages you say "skill-wise" you are fluent in, that's simply just you boosting your own ego again. Gee how smart of you to figure out that "Every case is different" all by yourself, how ever did you figure that out. Bottom line, WHO CARES ABOUT YOU? Your simply nothing more than what I flushed down the toilet this morning to me. If I don't live up to your standards, do you really think I would care?

In case you haven't noticed I don't even care if I'm being rude to you, simply because that's how you treat everyone else, and I see no reason not to treat you any different. But with your twisted mind, and huge ego, I would bet my last dollar that you think I'm jealous. Go ahead and keep that delusion if you wish, I look down on such pompous self absorbed people (as I flush them down the toilet).

    Bookmark   October 11, 2010 at 6:50AM
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Just put the Hydroton or susbtrate in acid water (water plus vinegar or another strong acid like sulfuric or nitric), wait for 6 hours to measure again the pH. If the pH is to high, add more acid and wait, repeat until the pH stabilizes between 5 - 6.
Write down how much acid are you using and how much clay you are cleaning.

Until then, you can use the hydroton with nutrient solution and check pH.

You should check if there are some bubbles when adding the acid water, maybe some carbonate is rising the pH. The carbonate may be present if this clay is old and used. The fungus and bacteria grow easily in pH 7 or high, acording to my experience.

Too sad the people use the forum to focus in arguing instead of focus in solutions. We find solutions helping other people, not in discrediting others.

    Bookmark   October 11, 2010 at 1:06PM
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after soaking the hydroton - 10 gals hydroton, 2 gals vinegar, 4 gals H2O I rinsed it and added it to my system. The ph has been steady at about 4.5 for the last 6 hours, but I am seeing bubbles and what can be described as "fizz".
So far so good, but what about the fizz?

James - it sounded like you kind of expected this to happen.
I didn't notice it while I was soaking, only after a hooked up the pump.

After speaking with a Physan rep, he assured me the fizz is a result of the Physan being a surfactant and will degrade into nitrogen after a few days.

Thanks again to everyone for the help. It's been a lot of work, but it starting to look like the end is near.

    Bookmark   October 11, 2010 at 4:03PM
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Hello Everyone,

@orgmacdonald : I am glad your problem was solved, as I suspected it was caused by the basic sites on the hydroton which have now been neutralized. This is a very common problem with this type of expanded clays which is increased when they are stored for long periods. For the past two weeks I did measurements of basic sites and surface area of a similar product to confirm this, as I suspected basic sites increase with storage time as a consequence of oxygen presence (storage in an enriched oxygen atmosphere increases basic site regeneration rate).

The fizz, as the rep mentioned, should a consequence of the decomposition of the surfactant you used which degrades as he mentioned not a product of carbonate reaction as this would have been observed earlier - upon acid addition - as james mentioned.

@lucas : I do not wish to make a part of the argument currently being carried out (side-tracking this topic) but I do think I must encourage you - without any offense intended - to look at how you are negatively contributing to this forum. Calling names and initiating such pointless arguments does not benefit anyone and in fact removes any possible intellectual benefit people may take from discussion that may be carried out here. Instead of putting the blame on others you should review the discussions you have participated in and how this has affected their quality and their point. Provocation and personal discussions do not belong in technical forums, especially when helping others deal with problems. So - for the sake of discussion - I invite you to become less offensive and more geared towards listening and helping. I do not mean to offend or lecture you in anyway but I encourage you to participate in a more productive manner :o) I will however refrain from commenting any further as this is just an opinion I want to give, not something I want to make this topic about.

Best Regards,


    Bookmark   October 11, 2010 at 9:03PM
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I am having the same issue. Pulled 15 gallons of hydroton out of my table and threw it in 4.8 water. Rose to 6.5 in about 20. Added more acid and took it down to 4.2 thinking that would do it. Woke up this morning (7 hours later) and it was 6.6!! In disbelief I took it down to 3.8 before leaving for work.
Should I be adding something else to the water? Hydrogen peroxide or perhaps some surfactant or rinsing agent? It just seems very odd tha it would raise the ph this much. Could be a function of only having about 5 gallons of water in the tub, but still. It's older hydroton but unused.

Any advice is greatly appreciated!!!!!!

    Bookmark   October 15, 2010 at 1:03PM
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To rule out the water completely I would suggest taking a qt. of tapwater to pool store and have them run a water analysis. If the total alkalinity of the muni water is fairly high:300+ppm repeated addition of a pH lowering agent are generally required. The service is generally free and it will give you a tremendous amount of knowledge regarding your water supply. New to board and to subject so I've learned much from this post thx.

    Bookmark   October 16, 2010 at 10:22AM
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I know this is an ancient thread, but in case another comes here looking for Hydroton help, I would like to share my knowledge as well. I am a graduate student in Botany, and have been studying exudation regimes of lupin roots. I need the substrate to buffer as little as possible to yield accurate proton exudation results. I too had a problem with hydroton going to pH 8 repeatedly. For more than a month I would bring the solution with hydroton to pH 5, and it would constantly creep up to pH 8. I had isolated all of the other factors out of the situation, so I contacted the manufacturer (General Hydroponics?). They replied that they were aware of the situation, and that I should use an acid with more buffering capacity that doesn't so readily disassociate ( I was using 1.2M HCl; (10% normal)). They suggested that I use citric acid, but alas, as this is one of the compounds I am measuring the exudation of, this is not a viable solution for me. I thought others may be interested in the Manf. suggestion. Personally, I will be switching to either a glass or plastic substrate such as Bio Balls (Coralife), with a neoprene lid to block extra light.

    Bookmark   November 17, 2011 at 5:15PM
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I know it's been awhile since anyone's posted here, but came across it recently and found some great info here, much thanks to Daniel's expertise.

Just a quick question about using the vinegar soak solution: does anyone know if will it also work with perlite to control cases of pH fluctuation?

    Bookmark   August 3, 2014 at 6:03AM
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I am new to hydroponics and wanted to thank everyone as I had no idea that the hydroton affected the PH. Great advice and questions from all. I really like the advice of omeyehead about taking the water to be tested at the pool store.

    Bookmark   August 18, 2014 at 7:43PM
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Holy Moly! I've come across this thread because I'm currently experiencing the same issues…HYDROTON causing the PH levels to rise almost immediately…using distilled water and no nutrients. My HYDROTON was sitting in storage for 10 years. I washed it very well with hot water several times and rinsed again with cold water. The rapid rise in PH continues. My next grow will NOT be using HYDROTON. By the way…this ENTIRE THREAD WAS AN ABSOLUTE HOOT!!!

    Bookmark   January 6, 2015 at 11:15AM
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