Hello speedfreakian,
Well first thing is that "recirculating run to waste system" contradicts itself. Run to waist does not get reused in the hydro system once it is pumped through once, where recirculating gets pumped through over and over. Anyhow it sounds like your using a typical DWC setup that holds 2.5 gallons. Using a pump to recirculate the solution (recirculating DWC). I know that they make a wide variety of swamp cooler pumps, but the ones that I am familiar with are not completely submersible. If it isn't completely submersible I would get one that was. It's just to easy to get electrocuted if not (especially kids, pets and other people). Bottom line, if you wouldn't feel comfortable throwing it in the bathtub with you, don't use it.

Is there a reason that you have the pump running 24/7? Like do they really like wet feet, are you not using much growing medium at all that would normally hold moisture? My basil plants didn't seem to like wet feet that much. For me cycles of 15 min on/off, or 30 min on/off usually is where I start, then I adjust as needed. I just look for signs of wilting, if so I water more. But that's really just a general statement, because I have no idea what temp and humidity is where your growing, not to mention what type and/or how much of growing medium you are using. I would only give them a 2 or 3 (30 min on) at most cycles during hours of darkness (starting 30 min before, and after they get any light). That's just one of those things where every situation is different, and every grower needs see works best in their situation. But that's where I start.

As for the nutrient solution, that can be simple or complicated. Fallowing the manufactures directions is great. Although you can probably mix them a little on the weak side, especially for small plants. I know this will cause a debate (I don't mean it to) but I wouldn't worry about PPM/TDS/EC. Especially for someone new, and with a reservoir so small. PPM/TDS/and EC measurement are just the relative strength of your nutrient solution. They cant tell you if the elements are balanced or not. And with a reservoir that small the bigger the plants get, the faster they will become unbalanced (more than a larger reservoir).

Just mix a new batch of nutrient solution, and change it every week or two. Then as long as you are using a good quality water, your fresh nutrients will be balanced again. Also if it's a 2 or 3 part nutrient, make sure to mix each one separately, and in the full volume of water you intend to use. If not they could bond together, and the plants wont be able to use them. PPM for basil is said to be somewhere between 700-1120, but everyone's growing conditions are different and will affect the actual PPM in your situation. You could add some diluted nutrient solution back to the reservoir (the plants will drink the water up) to the desired PPM, but that wont make them balanced. And the more you do that, the more and more unbalanced they will become (even at the desired PPM/TDS/EC readings).

The plants use more nutrients (depleting the solution from them) the bigger they get. So how often I would change them in the beginning, would mostly be based on how big they are. But with a 2.5 gallon reservoir for 2 basil plants, I would be changing it every week well before they got full size. pH and water level are what I would be concerned with. If the water level changes, that will change the relative strength of the nutrient solution (and thus PPM/TDS/EC). Less water, higher strength, more water, diluted strength. As the plants drink up the water, the nutrients left in the water becomes more concentrated. And the water level of a 2.5 gallon reservoir, for 2 full basil plants will fluctuate a lot. I would draw a line at the water level to keep track of it, just add plane water back (in-between nutrient solution changes).

pH for a reservoir that small presents another problem. Either rechecking and adjusting it every time you add water, or testing and adjusting the water before you add it. You also could store some already adjusted water in another container, that way you don't need to be adjusting all the time. But I would make sure the container was light proof, and I would add a small air stone to keep the water moving. I wouldn't want anything (pathogens etc.) to begin growing in stagnant water that I would in turn be adding to my systems. pH for basil is 5.5-6.5, I would just shoot for 6.0, that way it could fluctuate either way. I don't even use a meter for checking pH, I find the drops from General Hydroponics to be much less expensive to use. As well as more accurate, simply because the drops don't need to be cared for properly, and/or calibrated or you could be getting false readings.

Thanks for the reply, this is exactly what I was hoping for!
So I'll get a timer for the pump too, and then set it to run for 15 min on and how long off? I'm using those round, clay pebble things for grow rocks.
I've got a much better pump, I just need to find some bulkhead fittings to hook it up. then I could fill my reservoir much farther.
Ian

speedfreakian
If your timer has minimum settings of 15 minutes, I would start with 15 min on and 15 min off. That basically means it would be on for 50% of the time. If it has 30 minute settings, then I would start with 30 min on, and 30 off, again that's 50% of the time. The grow rocks (clay pellets) don't hold moisture as well as some other growing mediums like coco chips (and/or coir), but work well. That just means that they accommodate more air (roots need air as well). Of coarse that's only during light periods. I would water up to 30 min after the lights go off (and completely dark), and start again 30 min before they come on a gain. And probably a couple 30 min on cycles evenly spaced during dark time just for the heck of it.

But again with all the variables possible, I cant possibly give the exact best watering schedule. Even water temp and humidity within the 5 gallon bucket (with the roots) make a difference. As well as how much of the root system is submerged in the reservoir (water inside the bucket). It sounds like it's complicated with all the variables, but what it really comes down to is simple. Just observe your plants, they will tell you what you need to do. If they are wilting they need moisture and/or it's to hot (either air temp or water temp), and don't water more than necessary, roots need air just as much as water. That's why nobody can really give more than general guidelines, unless their there to observe your conditions, and why manufactures don't either.

I would simply suggest to start with the times I mentioned, then start watering less like 15 min on, and 30 min off. Observe the plant, and if it starts to wilt at all step it up again. Just play with the times, and observe what works best for your situation. Same goes for changes in the growing environment like temperature, observe how the plants respond to any change.

P.S. Like with any water culture system, you should also use a air pump and air stone inside the reservoir. The roots that hang down into the water need air also. Adding a air stone allows air bubbles to also saturate the roots inside the water (like I mentioned roots need air too), otherwise they can suffocate. A simple inexpensive fish tank air pump, and stone should be fine in a 5 gallon bucket. Like an air pump designed for a 15-30 gallon fish tank you can get at wal-mart for about $6, but if you can afford I would go with the 30-60 gallon pumps (they sell for about $12). More air bubbles never hurt, and you will most assuredly want grow more later.

If you're using small net pots, something along the lines of 15on/60off is more in order.
If you're using a larger volume of hydroton (those little clay balls) probably more like 30 minutes on /4 hours off.
that stuff holds water really well
The on cycle is determined by how long it takes to saturate your medium. the off cycle is dictated by how long it takes to dry out.

That's a great example of what works for one person does not necessarily work well for another. As well as the growing conditions being a factor. Those cycle times grizzmzn say works for him would never work for me. The smallest volume of grow rocks I have ever used is about 1 liter (4 cups), and even that had some coco chips mixed in for added moisture retention (that was a nightmare to separate later), and I couldn't let that go for an hour without seeing signs of wilting.

Granted I grow outside and the day and night time temperatures play a big part in my cycle times. And that's what I mean by growing conditions. But when the weather warmed up in June my cycle times during the warm part of the day when the plants (pepper plants) were in direct sunlight was 1 1/2 hours on and 30 min off. Even so the plants were on the verge of wilting until they were in the shade again. But at the same time the nutrient solution temperature was way to high (up to 90 degrees Fahrenheit), again a factor of growing conditions.

The next year I grew some tomatoes with a reservoir that was in the ground to keep the nutrient solution temp down. They remained between 74 and 82 all summer long. I was using a much larger volume of grow rocks, 2 gallons worth (32 cups) for each plant (no coco chips this time). Even with the much larger volume of grow rocks, 60 min without getting water and I would see signs of wilting. 30 min on and 30 off (my timers minimum setting was 30 min), and the plants seemed fine.

Just as an example, the same year I was growing some broccoli in 5 gallon buckets with coco chips and some coco coir on top. Total growing medium was about 4 gallons worth, and these plants weren't partially shaded by the tree like the tomatos. But because of the different growing medium my watering cycle was 30 min on and 2 hours off, even during the hot part of the day in direct sunlight. I never saw signs of wilting. In fact there were many times that I had unplugged the timer to for on reason or another in the evening, and forgot to plug it back in. Even without getting any water almost all day the next day, I didn't see singes of wilting. That never would have worked with grow rocks. I had those plants from October all the way until mid July before taking them out because all they were doing was flowering.

You may find that in your situation you can go as much as 4 hours without watering. Especially when the plants get big enough where the roots hang down into the water 24/7, then you may even be able to go longer than 4 hours without watering. And depending on the water level, you may not need to water at all. If the water level is high enough that the roots can wick up some moisture to the upper roots, that may be all they need. That's why I say that every situation is different, and just observe your plants and they will tell you what they need. Everything else is just a general guideline that may or may not work well.

HH,
Do you cover the tops of your net pots with some kind of plastic dome/sheet to limit evaporation. I know the plants transpire a lot of water, but the times you're talking about sounds more like an evaporation issue.

grizzman
In both situations I had plans to. The first one (pepper plants) were growing in upside down 2 liter bottles. I did use the bottoms that I cut off for a cap, but the center holes and slit that I needed to cut for the plant left sharp edges (because they would move in the breeze). Those edges began cutting into the stem of the plant, even in just about any breeze. The tomato plants were growing in 2 gallon paint buckets, I had planed to get lids for them and do the same thing, however never did. Not because I was thinking of evaporation, but contamination from anything and everything that is floating around in the air. Even from dead leaves that fall off and may get into the growing medium.

I know there is going to be some evaporation in our dry climate. However from the plants I have grown, I can see a direct correlation with plant size and water loss (use) in the reservoir, as well as the time of year. Because as temperatures rise, plants transpire more, sucking up more water at the roots. The bigger the plant is the more it transpires, there are more leaves and surface area to transpire.

And again in our climate the growing mediums ability to hold moisture is a big factor, and how that affects them. As an example the pepper plants growing in the upside down 2 liter bottles did not have much surface area for evaporation (the broccoli plants had much more surface area exposed). However the pepper plants would start to wilt within minutes while the sun was on them if I stooped watering (it was a flood and drain system). That's why I upped the watering cycle during that period. Even when watering for a continuous hour or more the plants leaves still felt limp, they would hold shape but felt limp. But as soon as they were in the shade they would feel firm again.

I cant tell you how much of that was due to the water temp, but I know that was a big factor. It especial showed with the tomato plants that had a in ground reservoir how relevant water temp was. But agreed, if growing medium is covered to limit evaporation there would obliviously be less evaporation. How much still comes down to growing conditions like humidity. We live in a dry climate with basically no humidity to speak of (unless it rains), that wont be the same in Florida where I hear humidity can reach over 90%. I don't know what are humidity is most of the time, my weather station always reads 20% (the lowest it goes) unless it rains.

Granted temp and humidity are much easier to control in a controlled environment, but even so everyone conditions are still different. An easy example would be the type of lighting, and how close it is to the plants. Even though the room temp may be good, the plants foliage may be experiencing high temps. Bottom line, even if you can determine the plants are wilting because on a particular watering schedule and the water is evaporating more. What you do but change the watering schedule and/or environment. It's not like I'm going to move somewhere that someone else watering schedule works for me. It's much easier to change the timer (watering schedule), and make that work for me.

An update.
I went to a nursery and got some English thyme, peppermint, chocolate mint, and parsley. I washed all the soil off and transplanted them into the grow rocks. All are alive but not exactly thriving.

I fixed up my reservoir so it now holds more like 4 gallons. I got another timer, so now the pump runs 15 min every hour. and twice at night. I wish I could figure out a way to show you guys a picture. the reservoir is a 5 gallon bucket below the plants, the plants sit in pots in a tray above the reservoir, not IN the reservoir.

I've been using Lemon juice to adjust the PH, it works pretty well. I've got the nutrients mixed according to the directions for the vegetative phase, 2 teaspoons for a gallon. (is this too strong?)

Just last night I noticed what looks like mold growing on the Chocolate mint's roots. Am I watering too much still? Also, the english thyme is drying out and dieing at some of it's tips.
Thanks for the help guys!