your system sounds more like ebb n flo or nutrient film technique, depending on how things flow. generally DWC is a static solution with air stones to aerate the solution. I'm not suggesting your system won't work, just that I'm not sure its really DWC.
High Nitrogen formulas will bring down your pH. high Phosphorus with raise it.
You shouldn't need to change your rez more than every two weeks or flush more than every 2-4 weeks. with DWC, the system doesn't need to be flushed. (flushed meaning fresh water run through it to waste)
I'm not sure you'll want to combine all those plants under one umbrella solution. I'm sure Jean-Luc will tell you its fine.
I don't personally grow under lights but everything I know or have read suggests CFL's aren't strong enought for tomatoes.
Can you provide a sketch of your system so I can see how it will work?
Also, I'd love to see some pictures once its up and running.
If you have more questions, feel free to ask.

Sounds like you are an old fish fancier, so you should know about high pH water coming out of the tap. In most cases it's done by adding lime to the water to avoid pipe corrosion.
You can bring the pH down by adding sulfuric acid (battery acid bought from the store diluted 1:10). The pH will bounce back several times until all the bicarb has been consumed, before it stabilises. It could take a few days. Best is to keep some stock.

The reason why i'm moving the water around, is that I can have a few different tubs that are linked together, and only have to test and maintain nutrients and pH of a single solution. The flow rate will be fairly low, perhaps 60 GPH.

Does a DWC really go two weeks with no movement of water at all? Hard core.

It's quite possible for me to run different solutions for the tomatoes then for the lettuce. What would you reccomend? I haven't bought nutrients yet, there is a hydroponics store nearby that i'm going to hit on Saturday

What is an old fish fancier?

An aside, will CFL's not work for tomatos, even if they are the high power 100w variety?

An indoor tomato will require 30-50 watts/square foot of plant crown to bring the plant to fruit.

Tomatos, on average, have a crown of 6-8 square feet. 100 w cfl lamp / 6 square feet = 16 watts/square foot, not adequate.

Ok. Is it sufficient to install 3 100w CFL's then? With reflectors? Or does the intensity of the light make an impact?

Ah! That makes sense (the flow in the DWC). I am planning something similar m'self.
In my current system, I change the solution every two weeks, add water generally once in the middle and the only water movement is where it ripples from the airstone bubbles. I don't test EC or pH with any regularity, but I have pretty good water.
As for nutrients, by a two or three part solution, so you can tinker with different blends, but don't buy too much. if you stick with it you'll probably want to buy volume soluble fertilzer to control costs. before I bought some big bags, I was using general hydroponics formula.
a fish fancier is probably someone who likes to raise fish.

Can you give me an example of Volume Soluble Fertilizer?

I was also wondering if you could add vinegar to lower pH?

Not quite sure why anyone though I raise fish... I've never tried and have no desire to...

Thanks for the info everyone. My seeds just arrived today, And tomorrow I go to the hydroponics store and get the rest of the system! Wish me luck!

25lb bag of soluble hydroponic fertilzer from southerag.com
50lb bag of greenhouse grade calcium nitrate

vinegar can be used. not sure how well it works for big shifts as I don't have to adjust things much.

not sure about the fish thing either, just speculating on what greystoke meant by it.

If you are going to use CFL's make sure you get both blue and red spectrums. ~6500k (blue) for vegetative stage and ~2700k (red) for flowering/fruiting... better off with a metal halide (blue) and sodium vapour (red) though.

Use reflectors on the lights unless you want the ceiling and walls to grow.........

Ok, I went, got some stuff, and started growing!

Here are some pics!

Just one bucket for right now. No reservoir like i'd planned because I only have the one tote to grow in right now, and I had difficulty finding the fitting I want. Whats a good way to go through the bucket to allow for the drain that is water proof?

I'm using 3 23 watt CFL's at the moment, which I know is woefully not enough. I'm hoping I can track down some 40 watt CFL's or find an old florescent ballast or something.

Personally I like to punch holes through the rez with this configuration:
{{gwi:997668}}
verbal explanation here
If the threads are too long to get a good seal (or the plastic too thin) you can either add another gasket on the otherside of the rez wall or trim the threads shorter. The latter being more difficult as you'd have to then refile the threads to ensure they work.

Thanks grizzman! I'll have to see if I can find those fittings and rig something up.

I've got a line on a guy selling used 400w metal halide bulb/ballast and reflector for $40, so i'm going tonight to take a look at them. If they are in good shape, i'm going to set one up, and start 2 tomato plants in a separate bucket. How far from the ground should I hang a 400w Metal Halide light. I'm told it will fairly effectively cover a 4x4 area?

The lettuce and herbs I planted haven't sprouted yet, but I guess it takes a few days, and I'm just a bit ancy.

Wish me luck!

I don't grow with lights, but I believe they say put you hands at the top of the plant. (or what ever height your checking)If its too hot to keep your hand there, the light is too close.
$40 sounds like a good price, just be aware, you might need to buy a new bulb. In fact, if you don't have a light meter, you probably should so you know the actual hours on the bulb.

I'm aware the bulb may be garbage, but the ballast and reflector is worth more then the $40 by itself. They're shop lights. Also: that's $40 Canadian, no taxes, no shipping, just go to the guys house and pick it up.

I picked up the unit. It's actually a brand new bulb! The guy took it out of the box, and put it in for me. His factory replaced a bunch of lights, and he made a deal to get these, plus all the spare MH bulbs!

I've hung my light in a temporary location. And all my lettuce that I planted on Saturday has sprouted! I'm psyched. Will these sprouts benefit from the high power light yet? Or should i keep em under the much less intense CFL's?

the brighter light will keep legginess down. just don't put them too close as the heat will damage or kill the plants.

I left the sprouts under the big light. Kinda hoping said light doesn't start a fire, as I left it hanging by one of those rubber bungee cords, and I think that light might get quite toasty.

Either way, I'm gonna start my tomato plants tomorrow! Gonna start three sprouts, and take the best two and put them in their own tub. Should be a good time! Wish me luck! I'll post pictures when i get something decent in size. Should I be giving these sprouts nutrients yet? So far they are growing in just water, but aren't big enough to transplant yet.

Lots to figure out here. Thanks for all the help everyone!

Hi Steve,

Don't be cheap with the sprouts (planted seeds), take a least half a dozen to start, even if you choose only 2 later. What if 1 of the 3 is not germinating at all (or delayed) and one looking week after a while?

I've tested nutrient requirements of tomato seedlings a while back for my own purposes. I've used 0.4 - 0.5 - 0.7- 0.9 and 1.2 mS (EC) from start (for germination even), no plain water for tomatoes with me...

The best results with the longest root size were the ones grown in 0.9 (total concentration of the NS. Even germination rate was considerably better from 0.7.
The formula used was my own tomato formula which has a ratio of 1-1.5 N/K, standard Ca, Mg/S and TE. I have good water tough, as low as 0.1 mS and a base PH of 7.1. If you do not control or correct your PH for the seedlings, a slightly higher nutrient concentration may correct the PH to the better and will make a difference. I do not agree with the "myth" that all plant seeds need to be started with water and very low nutrient concentration. This "less is more recommendation" is probably due to people who have terribly overdone it in the past or have had no EC-meter. But if the concentration is too low, you may give your plants a bad start and may delay development and potential considerably. If plants germinate and grow in nature, they do not do so in some low fertilizer soil or in plain water, - they do so in the very same environment as they'll grow up, don't they?

Another option (and safer method) would be to grow your tomato seedlings in a decent (professional) potting mix, repot them at 5-6 inches (or higher) in hydro by cleaning the the roots carefully from the dirt. I would even recommend this method for anyone who has little or no experience in growing seedlings in nutrient solution. It's anyway a good idea to have a few extra seedlings if the ones in the NS are not doing as well as expected, respectively to have a control group to compare.

Cheers
Lucas

I've added some nutrient solution to my seedlings, as per your recommendations Lucas. I mixed it at about half strength, as what i'm growing right now is lettuce. I was told that full strength might be to strong for lettuce. I'll up the concentration for when I do my tomato seeds once I can transplant these.

Keep lettuce at very low fertilizer rate to promote root growth (especially if nursing for NFT). Just watch the colour - only add a "pinch" (0.3-0.4) if they are starting getting pale or yellow in the longer run before transplant. ONLY with tomato seedlings I recommend higher nutrient levels (even) from germination.

PS: half strength... here we get lost in translation and semantics again.
The question is half (or only quarter) strength of what exactly...?!

I understand the fact that everyone sees and handles these measures, recommendations etc., in his own ways and by his/her own means very well. But then again, recommendations are even more inaccurate and confusing as the whole thing already is.

Let me put it this way to not get misunderstood: I do not criticize the way it is handled in many cases, but I obviously can't agree or correct anything at such degree of (in)accuracy. Then It's easier to stick with some common recommendations proposed at a multitude of websites and the standard replies of most forum members.

Best is to find your own "complete system" by trial and error and stick with the working one.

Good Luck
Luchas

The fertilizer that I am using is a 2 part solution. I think it's 2-0-1, and 0-5-3? Or something close to that. The full strength recommended on the bottle is 5ml / liter. Running half strength, i am adding 2.5ml / liter.

You can always use that 'half strength' formula, you can't do much wrong. Well, actually I'd recommend only 2 ml then. But lettuce seedlings are in fact quite tolerant. Most plants actually can cope and even thrive in/with various nutrient concentrations and formulas. The good part is, that you can't do anything wrong unless you clearly overdo it with the concentration. The bad thing is that you will hardly find out what really is (had been) best. Unless you do some sort of test with various nutrients and concentrations.

Unfortunately most people (beginners even less) have got the ambition and time to actually (and at least BASED on some scientific principals) put it to the test.

With tomato seedlings I found out that root development is delayed when nutrient is to week. Because the root growth and size obviously and continuously is adapting to the sprout/plant size. Hence too low concentration doesn't promote- but delays plant AND root growth.

Hint: do not fall for the phosphorus myth or for seeding formulas/products with high phosphorus (P) content. It's nonsense as seedlings do NOT need any surplus of P.

There is only one root and plant growth enhancing product I warmly recommend for any seedlings: any serious TRICHODERMA HARZIANUM based products ->

Here is a link that might be useful: International Society for Horticultural Science

I shall have to look into this idea lucas. From what I understand, peppers and tomato plants are both heavy feeders.

I planted my tomato and pepper plant seedlings last night. I added the same 2.5ml / l formula to them for now.

Something I noticed yesterday is that, my poor seedlings are cold. I measured the temp of the growth medium, and they were sitting at around 61 degrees. Pretty chilly by my standards. To warm them up, i've moved the light much closer, and now the seedlings are sitting at about 71 degrees. Here's hoping that is both a) helpful b)not gonna kill em all!

I doubt 71° is going to kill them.
Be careful running peppers and tomatoes in the same formula. Tomatoes will flourish in about anything. Peppers, however, will drop flowers if the Nitrogen is too high during blooming.

My intention was to cut the nitrogen component to both the peppers and the tomatoes when they are ready to fruit. I just checked, and my new tomato and pepper seeds (which are in a plastic bag, as per the instructions on the package of rockwool starter cubes) are sitting at about 81. This is much warmer! Is that ok for them, or do I need to cool them off?

I wouldn't go over 75. You might cook your little sprouts.

Look like i've killed my lettuce. I think i overwatered them? They kinda started falling over, and haven't grown the last few days.

I pulled one, and the root was fairly well developed and long, but the tip was turning black. I've started another couple, and i'm gonna leave em by and not water unless they go bone dry, and see how that does. I'm not gonna water the existing ones anymore and see if they recover.

I've also removed the tomatos and peppers from the bag, and dropped their temps down to 71 ish.

Just a hint stevey: do not change the conditions all the time and never change several params at a time. Seedlings are sensitive anyway, but what is worst is if the conditions change "drastically".

Most importantly: if you change more than one parameter (light, temps, nutrient concentration) and it goes wrong, you'll never know exactly what did cause the trouble and actually has to be avoided next time. And what you suspect being the cause, overwatering - may not even be close. In fact rockwool always, even if dripping wet, has air content - and too much water (only) shouldn't cause sudden death.

As I said, half strength says nothing to me, and it might have been too much in your case - especially together with increased temps. Anyway I suspect the change of temperature as being the main cause here.

You are doubtless correct lucas. I think i suffer from wanting my garden to get running faster then nature wants me to.

This is the action I have now taken, and i'm just gonna let it go and see how she does after this. I took the cubes, and dipped them in condensate from my dehumidifier. This water will have a pH of pretty close to 7, and be effectively pure. This should dilute but not eliminate excess fertilizer. I then placed them on a towel until they were no long wet, but moist.

I'm gonna sit back and see if they recover. Those that aren't pretty much dead are still standing upright. In the mean time i've planted 8 more seeds just in case the original batch die.

Am i supposed to leave them i the little plastic dome until secondary leave sprout? or take it off?

-Steve

domes are more important for root cuttings than for seedlings.

My plan is as Urbangardenfarmer states. To remove the dome once a day to let fresh air to enter, and to remove it once the seedlings sprout. I got some sort of fungas growing on my lettuce, probably because of me overwatering. It killed the seedlings. They just kinda fell over

I disinfected everything with a 1:3 bleach solution, and let it soak in nice and long. Then replanted everything to start again. Kind of sucks when I was hoping i'd have two weeks of growth by now, but live and learn right?

damping off seems to be a common problem with rock wool just based on my observations of posts here. I've had damping off problems with peppers but never with tomatoes. It seems toms have a hardier crown. you might want to limit your rockwool use to tomatoes in the future.

I'm only intending to start them in rockwool, then move them to hydroton in my DWC system. Is there another starting system that might work better grizz?

If this current version dosen't work, i'm gonna go get some good old fashioned soil to start my plants in, and then switch em over to the hydroponics system when they're big enough.

Hi Stevey,

I love growing tomatoes and peppers and a lot of other good things to eat in my indoor grow room.

I always grow my lettuce separate from my normal grow systems. I put them in a raft system in an unheated basement. As far as starting from seed goes for the lettuce, I just wet the hydroton and sprinkle a few seeds onto it just above the water level. They always germinate with in 24 - 48 hours.

Everything was replanted on Thursday and so far nothing has germinated.

Wait, you put a few seeds directly in the hydroton and they sprout in it? Funky... I would think the seed would fall into the water fairly easily!

In the raft system the water doesn't move around. The air stones kick up enough mist to keep the hydroton in the baskets damp. The lettuce seed just sticks to it. Lettuce likes it cool also, even for germination.

Well today is Thursday, tomorrow marks a week since I replanted everything. Nothing has sprouted. Not even a hint of any activity at all.

The conditions should be nearly ideal here, and i'm struggling to understand why nothing has sprouted. The seeds are moist, sitting at about 70 degrees, and under light. It's very frustrating...

Do not be too frustrated. I too am trying this out but with peppers, tomatoes and cabbage. I am playing with the DWC. I used the peat plugs on this try out for germination. Then placed them in the hydroton and the DWC. So far, things are gradually moving up. I like that method of sprinkling the seeds over the moist hydroton from postma.

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