Backyard Aquaponics
A place to discuss aquaponics

Hello everybody! I am ready to build my first AP system after studying about one year of Aquaponics food growing techniques. I am very excited.

I have a question to pose the community, but first a little on my system; My design is to be 230 gallons of water flowing through system. A 130 gal capacity sump with a 100 gal fish tank housed in a 10' by 10' greenhouse.

I want to construct both tanks with plywood framed with 2*4 pressure treated lumber and line the inside with a double layer high quality plastic pond liner. I am going to elevate my fish tank 1' above the sump tank to be very space efficient and allow access to the sump to change my pumps and heaters when necessary. The fish tank will be elevated on platform that rests over the sump held of 4"*4" pressure treated lumber decked with 2"*4".

So my dimensions for each tank will be 3*3 wide, and for the sump 2' tall and the fish tank 1.5' tall. I want to grow food year round out here, I am going to cycle with goldfish, but I have tank sized so hopefully I can do tilapia with this size tank. I plan to heat my sump tank constantly at 70 degrees fahrenheit.

QUESTION/ADVICE: Has anybody had experiences or successes framing their sump tanks and fish tanks as I have described here? I am looking for any experience and tips. I think that if I do a quality job with construction, the weight should be secure and I can have a long lasting pair of components for my system here.

Any input guys? Am I crazy to try and elevate 800lbs of water 4' off the ground?

Much appreciated

Make sure you use cross bracing on the legs and you should be fine. Triangulation of the load is the key to supporting the weight.

Diagonal bracing does reduce the free span of a beam but the load doesn't disappear. That load is turned into a lateral load on the posts so if the posts are not big enough they will buckle. Standard practice is to not rely on bracing to support beams. Rather beams should support beams and braces should brace.

I'm not saying it won't work but you have to be careful not to transfer the problem somewhere else. For example if braces are supporting beams these can place extra stress on your connections. Braces rarely fail but they can magnify the forces placed on connections causing them to fail.

Four 4x4 legs on level ground is plenty sturdy to hold 800 pounds of water, just not stable without cross bracing.

I appreciate the input everyone. I got three valuable responses here. Perhaps I will upload my sketch up for y'all to look at. I am going to move forward with this build this weekend. Thanks.

Vertically the 4x4's will hold 800 pounds fine. Only thing to keep in mind is when it is full of water and fish that are moving around there will be a lot of horizontal load on the stand, this is where the cross bracing comes into play. Make sure the 4x4s are all connected at the bases as well if they are not to be dug into the ground (optimal), and cross brace as many of the corners as you can.

A sketch would be good as it is hard to imagine what someone else is thinking.

Great post. I will definitely over build this thing. Thanks everyone I am beginning construction today, starting with grow beds. Will have 26 sq feet grow bed available.

Okay everyone I have a new question to pose to the community;

What is the recommendation for plastic lining in grow beds, fish tanks and sump tanks?

I know duraskrim works well for the grow beds, I think that is what I will order for those. The duraskrim won't size enough for my tanks, who has had success with what plastic pond liners for tanks and AP system use?

Thanks

I would use a rubber pond liner in lieu of plastic. It is less likely to crack and leak and is much easier to repair if you do somehow put a hole in it. You can find it all over the place, even the big box home improvement stores carry it. Online would be cheaper.

Almost everyone has used pond liner, and if I'm not mistaken among Duraskrim's uses there is also "pond liner"

If you meant plastic sheeting instead, like the 6mm used in construction for example, I wouldn't use that but have never actually tried myself

Keep us updated. I am curious to see what you come up with.

What size (thickness) plywood do people find won't bow for building grow beds?

3/4 with cross bracing under it would be best.

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