Backyard Aquaponics
A place to discuss aquaponics

Hello to Forum Members,

I'm new to aquaponics, having recently read the majority of Aquaponic Gardening by Sylvia Bernstein. About 20 years ago I had a home-made pond of 650 gallon (2500 liter) capacity. A 50-gallon (190 liter) drum served as an external biological filter.

Now I have a small 6 X 8 foot glass greenhouse, that I'm fitting with an aquaponics system. Likely I'll construct my own fish tank and grow bed, using 3/4 inch (1.9 cm) plywood and either potable water epoxy or perhaps pond liner film. I'm in the planning stage and want to do things right.

I want the fish tank to have as much as 100 gallons. To fit within the existing space the following will give around 100 gallons (380 liters):

Base = 22 X 35 inches (56 cm X 89 cm)
Height = 33 inches (84 cm)

This brings up a question:

Is the 33 inches (84 cm) depth excessive? It gives maximum gallon capacity for the available space. But I want to be sure that there are no problems with such a depth.

My 50-gallon grow bed will also be of 3/4-inch plywood - 22 X 46 X 13 inches (56 X 117 X 33 cm).

Thanks for any advice and help you can offer.

Best Regards,
Russ

Hi Russ, welcome to the forum!

I don't see any problem with the height.

Think about the many thousands of people using IBC totes for fish tanks, I'm pretty sure they are well off the mark of the proportions recommended for aquaculture tanks or ponds.

And, I believe that many stock tanks are close to that height as well.

One issue I can think of related to depth could be if you are trying to pump air in with a weak pump. The water pressure might cause the air pump to have a hard time delivering. In these cases, a lot of folks simply adjust the depth of the airstones to achieve a better airflow.

The key with any wooden pond is building it with enough bracing or in a way that will withstand the force of the water pressure from the inside. I think that is a bigger challenge to consider, and maybe you already have.

What kind of fish are you planning to use? Certain fish might do better than others in your given dimensions.

Are you including a sump?

How are you planning to configure the system? Do you have a sketch or plan you can post?

It might inspire others to chime in...

Thanks so much for your reply, Los Angeles Will. I will give some more information about the planning for our aquaponics systems. My wife and I have been aquarium and pond aficionados for some years. But aquaponics offers a way to better utilize our small greenhouse and grow some nice dirt-free produce. We presently have a large vegetable garden of sixteen 8-foot X 2-foot raised beds. While it produces a large amount of organic produce, the monthly water bill makes for expensive vegetables. This is especially so for our sandy soil here on the Oregon coast.

This year we have kept a large flower pot (perhaps 20 gallons) in the greenhouse with a few feeder goldfish. Just some wild watercress with air-pump bubbler has kept them alive. During the summer they were fed 2-3 times a day. With colder weather, I've ceased feeding them.

Now I'm working on plans for an aquaponics system. So I appreciate any help you can offer. I've read a lot in the above mentioned book and on line. So I feel as if I can proceed with construction of the wooden fish tank and grow bed. I will be adding extra 1-1/2 inch thick wooden straps around the fish tank and grow bed to help resist water pressure on the 3/4 inch plywood.

Would A-C grade exterior plywood be sufficient for the tank? I plan on coating with potable water grade epoxy paint on inside and many coats of exterior paint on the outside. Seems like epoxy on the bottom outside would be a good idea since it will be close to potentially moist soil. The fish tank will rest on concrete slabs to give support and separation from the soil. I may put a layer of 2 X 6 fir boards under both tanks for added support. Pond liner film is another option. But I'm not keen on the folds necessary in corners. Any thoughts?

I would like to make the fish tank as large as possible, even though at first there will not be matching grow bed volume. My aquarium background tells me the more gallons for the fish the better for the water quality. So what fits in 1/2 of the greenhouse length is about 90 gallons (45 X 19 inches base, and 26 height). The gross grow bed volume is 60 gallons (24 X 48 X 12 inches). Seems like stocking with fewer fish would compensate for grow bed to fish tank mismatch. None of the Rubbermade stock tanks will fit in the greenhouse.

Do you see any problems with that thinking?

I plan on buying quality, large capacity water and air pumps. Also the fill and drain system via siphon would be simple and less problem prone. The planned for dimensions of fish tank will give room for plumbing to return water to fish tank. The grow bed will be supported by concrete blocks at the same level as an 8-foot bench on one side of the greenhouse. My little green house is just 6 X 8 foot. Half of it has dirt grow beds for basil and peppers on the sun side. On the back side will be fish tank occupying 1/2 of the length with grow bed above for the other half.

Not sure what fish to start with, but perhaps shubunkin goldfish. With some insulation around the fish tank and back of the greenhouse, we might opt to heat the water to tilapia temperature. I don't know if the 19-inch X 45 inch base will present problems for larger crop fish.

I have attempted to attach a schematic drawing of what is presently planned. It's a bit cramped. But to get under 900 pixels at 100 DPI scan - well there it is. Thanks for any help and advice you can offer!

Kind Regards,
Russ

Hiya Russ, Will has shared good advice and I’ll add my 2 cents.
You’ll need good access to your fish tank if you plan on eating fish and a cover of sorts as some fish like to jump.
You might like to factor in plans for expansions as I think you’ll find you’ll want more growing space. Perhaps grow towers and nft;)
Keep us in the loop and good luck.

Thanks for the comment, skeggley. You've added some useful information. So a waterproof 1/2 cover of some sort would be beneficial to give a hiding place for the fish. I forgot to mention the bench in my drawing is just an open wood frame with removable wire shelf on top. So access to the fish tank will be there. I could even place the wire shelf on top of the fish tank to let in light, and keep fish inside.

What is meant by "and nft"?

I was just discussing with my wife about adding some vertical pipes above the grow bed for extra planting space. Having a powerful pump for the added head would be necessary. Also some added grow volume could be added with horizontal pipes at grow bed height around the rear side of the fish pond. But such additions will come later. It is a bit of a challenge getting it all inside an 6 X 8 foot greenhouse. Half of the available space is already in use with dirt-filled beds.

Thanks for your help!

Best Regards,
Russ

I don't see any problems with your thinking, the fact that you're thinking is a good thing!

Some people have problems with light stocking, and not having enough nutrients to grow what they want.
A lot of people start out with plants that require less, in which case a lighter stocking would probably be ok.

Room to grow is a good thing.

How much space do you have from the planned height to the roof of the GH?

Maybe sinking the tank in the ground could work for you to give more height above the bed in case you want to grow taller things down the road?

Lots of people don't have problems with folds in the liner, and there are some nice tutorials on youtube about how to fold a really tight liner fold.

Epoxy or something similar/ paintable rubber would probably be fine with enough reinforcement at the seams. I agree with coating or wrapping the bottom of the box as well. especially if it's close to the ground.

Have you checked craigslist/ offerup for your area? You might be able to find something suitable for a fish tank on there.

As for the tilapia, it might be easier to go with bluegill, I think that is what Scotty uses, and he's a little more inland I believe. They might be easier to obtain, and definitely easier to keep heat wise. The only thing is that they grow somewhat slowly. There is a hybrid bluegill crossed with another sunfish, which is supposed to grow bigger and faster.

As Skeggley said, keep us in the loop...

Oh, and he might come back to it, but NFT is Nutrient film technique, where you pass a thin layer of water through a pipe and the roots dangle into the water, plants are in a net cup or similar, from my understanding. I've never tried it though.

Thanks for the reply, LA Will. Now I'm getting dangerous with some more thinking. I've decided to remove the wooden bench in the greenhouse. It would serve no useful purpose and just made for obstacles to be worked around. With the bench out of there, the entire north wall is available for aquaponics. There is still a 4x4 post in the ground that provides support for underground water supply and GFI electrical outlets. These will be handy for the aquaponic setup.

With the added space my fish tank could increase to 100 gallons. The grow bed stays at 60 gallons, situated at suitable height on concrete blocks. There's not much overhead room at the back of grow bed because the roof slopes down from the center walkway peak. So the grow bed in the green house will not accommodate very tall plants. Maybe your suggestion of sinking the fish tank below ground is the best way to go. But we may well install some Nutrient film technique plumbing to increase grow space. Hmm - more thinking will be needed.

There's so much information online and in the Aquaponic Gardening book I have. But I believe I have enough information to eventually get going with this. My wife is very supportive. After all she originally purchased the book I'm reading. This forum looks to be a gold mine of useful information as well.

I stumbled across this website while looking for sources of Tilapia - https://lakewaytilapia.com/How_To_Raise_Tilapia.php. The amount of information about Tilapia is impressive. Also the price for 10 mixed sex Blue Tilapia is reasonable - $33 including shipping. The plans they have for building a 600 gallon Tilapia tank have got me reconsidering some of the details of my own fish tank. Now I'll be spending the extra time and expense to construct a tank that won't fail over the course of some years. It will be well braced, insulated and lined with white, food grade pond liner. Below are a couple of photos from Lakeway's tank-building instructions.

But with pandemic conditions I'll see about home delivery of a couple sheets of 3/4-inch plywood and perhaps some 4 X 8 X 1-inch sheets of styrofoam insulation. The back wall of the green house needs insulation. Also the fish tank and grow bed would benefit from insulation to keep heating costs down. But electricity is cheaper than water, even here in the rainy Pacific Northwest. So the reduced watering requirement of aquaponics will be a saving.

So that's what I've been thinking. Any comments or suggestions?

Russ