Frequency of Cycles

crafting4goddess(5)November 22, 2008

Being new to Hydroponics, I have gone out far & wide to learn all I can right away. One conflict I am running into is the frequency of cycles that should be done in an ebb & flow system. Currently I am running a 15 minute flood cycle every 3 hours, 24 hours a day. Now I read that flooding should not be done at night because the plants reverse their CO2 intake to O2 intake at night. I've seen no adverse effects to my plants with the current cycle I am running, so should I not worry about running, or not running, it at night?

Another question I have is...

Can rockwool cubes be recycled/used more than once? That is what I am using at the moment because that is what came with the starter kit I purchased from the local Brew-n-Grow. If they cannot be used more than once, then I cannot see using them to be efficient nor less wasteful. I'm thinking of switching to gravel as it seems to be easier to plant, pull, and replant in....although it would weigh much more.

Thanks Much!!

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To answer your questions-

There is no harm in running flood cycles at night. Most plants do not absorb a meaningful amount of water or nutrients during the night but you aren't hurting them by allowing the flood cycle to occur. Think about plants growing outdoors- does it seem to hurt them if it rains at night rather than during the daytime?

Generally rockwool cubes can be reused at least a few times for hobby level hydroponic systems. I let mine dry out completely and remove any pieces of old root that are protruding from the cubes before replanting. The main advantage of using rockwool is not low cost or reusability though, it is widely used because it has a very desirable moisture/air ratio. As with any growing media- reuse can increase the posibility of disease if not properly sterilized between plantings.

Gravel is reusable, inexpensive, and widely available but as you mention it is quite heavy. A lighter weight alternative would be using expanded clay pellets which are often refered to as "Hydroton**". These pellets look very similar to pea gravel but hold a better air/moisture ratio and weigh considerably less as well.

**Hydroton is a brand name that has become a catch-all for products of this type in much the same way we call any tissue a Kleenex regarless of the actual manufacterer.

    Bookmark   November 25, 2008 at 9:51AM
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Ahhh, yes that does make sense now that you put it that way. :)
So then it would not hurt to not have the pump run at night for approx 8-9 hours. Great! Less evaporation to deal with & less electricity to use.

Hydroton, I have some of that from the starter kit as well. I'll have to dig it out & apply it to some of my ideas for smaller hydro units. :)

Thanks much for the info!

    Bookmark   November 25, 2008 at 11:32AM
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Rockwool can be problematic to re-use, but it can be done.

Skipping the night flood cycles is fine, as is letting them run. It's mostly a decision of what works best for you. Personally I'd be inclined to run them rather than skip them.

Be sure to ask any questions you've got, everyone around here is really helpful.

    Bookmark   November 28, 2008 at 10:57PM
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greendude(Arctic Wisconsin)

Hello, I run an Ebb & Flow and it took me a while to settle on a set cycle for the flood. I started with 4 times a day (every 6 hours) until I noticed a lot of mold growth on the tops of my rockwool cubes, so I cut back to 3 times a day (every 8 hours). Then when my plants got bigger I noticed they seemed a bit droopy, so I increased back to 4 times a day and conditions seemed to improve. A 3% Hydrogen Peroxide spray around the base of the plants every other day or so keeps the mold at bay.

Of course, your mileage may vary, as everyone's setup is a little different; your plants will let you know if they are getting too much/little water. As far as I'm concerned, I prefer to run the cycle at night just so the roots don't dry up (I haven't experimented with omitting the night cycle but I don't want to experiment now that I've put this much effort into keeping my plants alive and there is actually fruit on them now!).

Rockwool seems to me like it could be reused, but mine is so full of mold and algae on the surface (and maybe below the surface) that I don't think I want to reuse it. I have several more cubes for my next batch of plants, and after that I think I may go with coco coir and/or hydroton in net cups (although that will completely change the dynamic of my ebb/flow cycle).

Good luck to you!

    Bookmark   December 2, 2008 at 4:19PM
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That's a good point, you may have to adjust your cycles as your plants mature.

And hydroton is definitely a better medium if you're concerned with re-using materials.

Another thing you can do to combat mold and algae growth on the top of your medium is to cover it with a white or reflective shield to limit light exposure. If you cut little notches for stems and use two pieces, one on each side, you can make a nice adjustable cover that will keep enough light out to discourage algae without hurting your plants.

    Bookmark   December 5, 2008 at 8:33PM
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