New to hydroponics. Need help with DWC!

JentzOctober 21, 2012

Hi, everyone!

I'm new to the whole hydroponics thing. Well the whole gardening thing really. I am in the process of setting up my own Recirculating DWC system. My seedlings have already been started and want to get the system up and running before I have to transplant them. I have a few questions for you guys!

I already bought the growing containers I need, Which are 11 18 gallon totes and 14 5 gallon buckets.

The plants I have are rosemary, thyme, basil, cilantro, lettuce, kale, romaine lettuce, cherry tomato, carrots, onions, Marvel peas and bell pepper.

Inside the 5 gallon buckets I plane to put the bigger and taller plants in, such as the tomatoes and peppers, one per bucket.

The smaller plants like the lettuces and herbs will go inside the 18 gallon totes, 6 plants per tote.

1)Will 6 plants per tote be okay?

2)How many GPH of water does each plant need?

3)What is the flow rate each plant need?

4)What size reservoir?

5)How big a pump?

6)How big do the net pots need to be for each plant?

7)How big does each of the plants root systems get?

8)What should the water level be in each bucket and tote?

9)Where should the return line hole be on the bucket and totes?

I've read that hair should be pumped into the water so the roots can get oxygen.

10)Should the airstones be in the reservoir or inside each of the grow containers?

11)How much air needs to be supplied?

12)What size pump is required?

I believe those are all the questions I have. If I think of anymore I'll let you know. Any help is very much appreciated! :)

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I mean this in all sincerity; For that many questions, you're growing too many plants.
The smaller plants need 8"-12" between them. So if that works with 6 per tote, then great. I wouldn't plant rosemary closer than 12". I have a plant that's been living for about 4 years and it fills a 12x12 easy. Also, tyme is a somewhat spreading plant so be careful not to plant where another plant will shade it out. I'm not familiar with marvel peas, but the snow peas I'm growing don't take a particularly large surface area but they are a vine, so figure out where that vine will go. Similar thing with tomatoes.
In a pure DWC, I've grown everything in 2" pots. I have a couple of 3" pots I use from time to time, but you really don't need larger than 2" pots.
The key to DWC isn't so much GPH as it is aeration. you only need enough GPH to ensure the plants don't consume all the oxygen in their bucket before it is replenished. I suspect one change per hour is more than ample so you can do the math to figure that out.
Ideally, in Recirculating DWC (rDWC)you want to aerate the primary reservoir. While this can be done with air stones, a more simple means (since you're running a pump anyway) is to create a waterfall where the water is returning into the primary reservoir. Let it fall 6" to 12" and it'll give you plenty of aeration. Pump size will be dictated by: how many GPH you need and how much head you need. Head is how high the pump must lift water above the primary rez level.
The location of input and output lines has been the subject of some debate here. IMO, you want the input line to discharge into the secondary rez near the bottom of the bucket/tote on the opposite side from the return (output) line. the return line will exit through the container near the bottom but will have a 90° bend inside the container will a length of pipe running up that will dictate the height of the rez in the secondary container. ( similar to how ponds control water levels). The idea of opposite depths and sides is to ensure that all the water is replenished. If you dump the water in at the top of the res, even on the opposite side, only the upper level of the nutrient will recirculate and the lower depths will soon run out of air. this is known as laminar flow.
The level you need the nutes at in the secondary rez is somewhat preferntial. You just have to ensure the plants roots stay damp until they work there way down into the nutrient solution. That the nice thing about the elbow detail I mentioned above. you can easily change nutrient levels by simply adjust the height of the vertical tube.
Of course, if you intend to change nutrients a lot, this system can be taxing. you'd need to remove said vertical pipes each time you changed nutrients to ensure most of the nutrient in the secondary rez's are removed. There are other options for a rDWC to prevent that by basically letting the primary reservoir be higher than the secondary ones. In that instance you're essentially using your pump to lift the water into the primary rez.
Your reservoir should probably be double what the entire system needs. what is "needed" is enough nutrient to fill each secondary rez to its max height plus enough to fill all the water lines and keep the inlet line of the pump submerged. Again, that's just doing some math w/ a bit of fudge factor.
I hope that helps. Feel free to ask more questions if you have them.

    Bookmark   October 22, 2012 at 8:42AM
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When you say "cherry tomato," there are over a hundred different cherry tomatoes. Most of them are indeterminate and not what you want. It will work better if you grow a compact determinate. My favorites for container growing right now are Terrenzo and Bitonto. Lizzano and Tiny Tim are two more.

Regarding your system, you should probably choose between green leafy crops and fruiting crops, and not try to grow both in the same system. They do best with different nutrient mixtures and different artificial lights, if your system will be inside. It's easier to grow leafy crops; you might start with those first. If you want to do both at once, then built two separate systems.

    Bookmark   October 22, 2012 at 12:20PM
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You may get some good info from this video on a DWC and the size questions may come into play. Link is at the bottom.

As grizzman stated, you are asking a multitude of (all good), but may want to slow down a bit and re-evaluate your grow and the space you have available.

I say that in light of the fact that I tend to over load the system as well!


Here is a link that might be useful: Deep Water Culture Video

    Bookmark   October 22, 2012 at 12:48PM
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I have to say that you're more ambitious than I am. I routinely grow many of the plants you name in a much simpler manner. My basic unit is a four gallon tank of nutrients with a single fish tank bubbler. Lighting is from a double 14Watt CFL mount in an aluminum reflector that started life as a five inch drier duct pipe. I grow leaf lettuce, spinach, Bak choi, cilantro, and basil in disposable three ounce bathroom cups with holes drilled in the bottom and filled with Coir. These cups are supported by three quarter inch styrofoam floats with holes cut at appropriate spacings. For a nine by fourteen inch float that amounts to eight to ten plants per unit. I take individual leaves from lettuce, Bak choi, and spinach for daily salads and keep a number of new plants started to replace the older as needed. The herbs need to be spaced a bit more widely but can be kept short by trimming for use.
Tomatoes, peas, and peppers present different problems because of height but I have done these in larger baskets and in the summer where lighting is less of a problem. The root veggies have been only limitedly successful in ebb and flow but I'm told that it can be done. Hope this helps.
Hope this helps.

    Bookmark   November 23, 2012 at 4:48PM
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Are you growing indoors? What kind of lighting do you have? Do you have an exhaust fan and oscillating fan(s)?
As a sidenote, I agree with grizzman. For the number of questions you have, your system is far too large. While hydroponics allows for careful plant management and excellent rewards at harvest time, it is more difficult and time consuming to manage when compared to growing in dirt.
Each plant has specific nutrient requirements (as mentioned by Cole_robbie), and this not only varies by species, it also varies based on whether it's flowering or growing vegatatively. Mixing a range of plants in the same system is a recipe for disaster. Larger plants require higher nutrient levels, and the NPK ratio changes during fruiting/flowering. Levels for a large plant would harm a small plant, and levels for a small plant would starve a large one. Some need additions like calcium or magnesium, while others don't.
When you flower your tomatoes, peppers, (?peas?) you will have to lengthen your dark (night) cycle(plants don't care about length of day to trigger flowering, only length of night). This change, unless you have segregated grow rooms/chambers, will likely cause your spices and leafy vegetables to flower as well. I'm not sure of the effects to root vegetables, but flowering changes and sometimes ruins the flavours of herbs. Basil, as an example, becomes bitter when flours appear and they should be pinched off as soon as they appear if you aren't trying to get next crop's seeds.

1. The number of plants per tote depends on a few factors. Size of mature plant is the most important, although you can do much denser if you want to do an extended harvest of young greens. I'm growing 30 basil plants in a 15 gallon DWC with a 150w HPS and 2 42w (6400k) CFL. I'm using 2" net cups, spaced like a cloner.
2. Varies greatly by plant size, higher with larger plants. Add air stones in to every bucket and tub, as well as the reservoir.
3. This is the same question as 2, but I'll take this time to mention that all of your setup needs to be sterile before you use it, and all water bins, lids, and pipes need to be completely opaque. If it's translucent (any light gets through), you'll likely have a downhill battle with algae and/or root rot. Spray-paint it black then white, or return it and buy opaque stuff. Seriously.
4. Someone covered this, but you also have to keep in mind just how much water will be used on a daily basis. Having a reservoir that is the volume of the full system might not last for a whole day when your plants grow up. You need to maintain a high enough level to stay above the pump, and also to not cause the water to be toxic. Plants don't use nutrients and water at the same rates, so over time your solution will either increase or decrease in concentration. At high concentrations, some plants will die. Think of it like this, we (mammals) need salt to live. If we're stranded on the ocean, we will die of thirst because the water is too salty for us to drink. It would dry us out just like too-strong nutrients will starve and kill a plant.
5. Your pump just depends on your target flow rate. I've done 6 outdoor top-feed tomato plants, and a pond pump was more than I needed. I'm doing DWC now, but not recirculating, and I don't have relevant experience.
6. Net pot size depends on plant size. I'm using 2" for basil, but I would go for 4-6" for larger plants. The most important consideration is that you are able to block light to the roots with hydroton and maintain plant stability. e.g. basil would do just as well in a 6" pot as in a 2", but tomatoes in a 2" pot would destroy the pot and likely fall over.
7. Varies by plant, but they will grow to be as big as they need to be. In a DWC, don't worry about how big they will get. You'll be fine. You do need to make sure that the roots don't grow in to your pipes (they will surely try) and block the drainage. Think flood. That's another reason to not try to have everything on one system. A single failure could kill your entire crop.
8. For baby plants without roots outside of the net pots like clones and new transplants, water needs to be high enough to keep the plants wet. If you're starting seeds or clones in rockwool, put a layer of hydroton in the bottom of the net pots, then put in the rockwool. Fill beside rockwool cubes with hydroton. Water should touch hydroton, but not rockwool. When first roots start to hang down, water level should be lowered to a bit below the net pot bottom. Leave a bit more space if you're crazy enough to not put in an airline and stone to each bucket.
9. Both/All.

  1. 1 stone in each bucket/reservoir will be enough, but some people will say that more is better. There is a saturation point where no more oxygen can be in the water, and it depends on temperature (colder = more dissolved oxygen).
  2. The pump needs to put out enough for each stone, so you'll need a strong pump (or a few weaker ones). Don't quote me on this, but a rough estimate might be about 10w per air stone. You'll also need to take in to account the length of air tubing (longer requires higher pressure) and depth of water (deeper requires higher pressure). Separate pumps will help when one fails as well (and it will).
    Hope that helps!

Here is a link that might be useful: DotCaDot - DWC Sweet Basil

This post was edited by Seven_Six_Two on Mon, Jul 7, 14 at 22:28

    Bookmark   December 16, 2012 at 4:36AM
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That's a lot of words. The only part I would contradict is that you CAN use 2" net pots for tomatoes. as they always have to be supported from above, due to their size, you're not relying on the weight of the net pot to stabilize them. the roots will grow just fine down into your reservoir and that's where the bulk of them will grow anyhow.
Now something like a green pepper may warrant a larger net pot as they need to be bottom stable (don't normally stake them) but smaller plants or plants that will require staking don't need larger than 2" pots.

    Bookmark   December 16, 2012 at 10:12AM
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Strings or wires as supports can maintain just about any sized crop while using small net pots and low amounts of hydroton or silica.

I've found the wire tomato cages do a great job when fashioned upside down with the base bent to accommodate the reservoirs.

I've seen some really neat wire and string set-ups as well, but plenty of bracing is needed to prevent sag.

    Bookmark   December 16, 2012 at 10:28AM
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Thanks for staring thread & replies for the related query which is very helpful for grower.

    Bookmark   January 23, 2013 at 6:05AM
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Keeping it simple is always a good idea and beneficial at the front end of the learning curve.

Read and watch everything you can and then begin putting it to use.

I have found that using a journal in just about every technical hobby has been a key to success.

Speaking of of success to you!

Here is a link that might be useful: My Indoor Growing Adventure

    Bookmark   January 23, 2013 at 7:57AM
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Hello all,

seven six two,

did I understand you right not to get the rock wool wet when placing in the dwc. I placed a layer of clay pellets in the bottom of the net pots and then placed the seedllng rock wool in center. I then placed clay pellets around the seedlings. Hope this is correct.

my plants in the rock wool have been partially submerged in the dwc platform for a few days and look good right now, not sure what the eventual outcome will be, since this is my first.

Thanks for any input

    Bookmark   November 8, 2013 at 8:35PM
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That sounds about right. I use hydroton under and around the rockwool in the net pots. When the plants are young, I keep the water touching the hydroton, which wicks the water up to the rockwool, keeping it damp. If the water is touching the rockwool, it is too high and the rockwool will be soaked. That's no good, because then there is no air available to the seedling and it might die before the roots can grow. If you check the link to my article (updated) at the bottom of my original post, there is an animated gif which shows the inside of my system after harvest. If you're quick, you can see the hydroton in the last frame.
>> Grizzman - That makes sense. Have you grown a full size indeterminate tomato plant in that size cup?

    Bookmark   July 7, 2014 at 10:37PM
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I sure have. this is a 20 oz mortgage lifter I grew in 2" net pots/

Was taken in 2009. I've had terrible problems with horned caterpillars since then and have dramatically cut back on growing tomatoes. But that is not the hydro's fault :-)

    Bookmark   July 8, 2014 at 10:14AM
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