Backyard Aquaponics
A place to discuss aquaponics

Hello all, from Vancouver BC Canada.

You may recall from my new member introduction post, that i'm building a 14x20 greenhouse to house some in ground grow-beds and an AP system.

I'm stuck going back and forth between a simple barrel-ponics type recirculating system and a constant height tank with sump etc.

Now, being i'm an analyst geek, the added complexity of the sump type system appeals to me, but i have some questions.

first off, i've attached an image of what I think the layout will be in the greenhouse. this was an earlier version, and i've since enlarged the tank and moved it to the wall rather than being in the middle. (Use it to visualize and frame my thinking here).

So what I have now is a ~2500L tank, 9'x4'x3'.

In the first scenario i am thinking that I would just pump the water from the tank into grow beds on a timer, and let them drain back into the tank.

in the second scenario i'm thinking of having the tank overflow into a sump, and then pump from the sump into the growbeds.

My question is around the accumulation of waste in the tank. If i'm pumping directly from the tank, I would think the circulation would be improved as the waste would flow into the pump and be run through the beds etc.

In the constant height setup, the overflow is simply going into the sump, so the fish waste isn't really circulated and is allowed to settle into the tank.

How have folks here dealt with this?

What setup would you recommend, given my tank and proposed setup?

Oops.. attachment never made it.

What sort of grow beds will you be using? Will they be higher than the fish tank or lower?

The best configuration IMHO is to pump from sump to fish tank and for fish tank to overflow (via ventruri drain) to the grow-beds. This means that you still achieve the one pump, constant height in fish tank model, but the solids are moving from the fish tank to the grow beds. Issue with this for you is that the tank must be highest, followed by grow-beds, followed by sump. If you can sink your sump and raise your grow-beds a bit, then this is achievable.

If you sink the tank only a little way into the ground, then have the grow beds sitting on the ground (so the water level in the fish tank is a few inches above the top of the grow beds) then sink the sump tank down into the ground, then you could do the constant height in fish tank draining directly into grow beds. I agree that a venturi drain from the fish tank into grow beds is the best option for getting solids from the fish tank to the grow beds without mucking about with solids in the sump. You just need to make sure that the pumping action from the sump into the fish tank is strong enough to stir up the water and solids enough that they will flow out. Most sump pumps are energetic enough for that.

IMHO stiring up is not the prefered option. The best is to create a whirlpool action (albeit mild), moving solids to the centre where the venturi drain is ideally located.

Whirlpool action is more what I meant but that is a bit difficult in a non circular tank.

Hi all,

The tank as pictured is 1' (30cm) below grade. 2' (60cm) is above grade.

So really, the tank is the lowest part in the setup.

I was thinking the grow beds would be mounted on top of the fish tank, and the water flow would be as follows;

Pump from Sump -> to Settling (raft/nft/duckweed) Tank -> drain to holding/flush tank -> flush from holding tank to beds -> drain from beds to fish tank -> overflow from fish tank to sump <repeat>. (See Attachment)

My plan is to use 1000L barrel/drum tanks of dimension 40"w x 48"d x 46"h (pictured) for the other components in the system.

Do you think this would work?

Are there any issues with covering up the fish tank? i.e. does it need sunlight?

NFT before gravel bed ,, not ideal.

I'm not saying it won't work ,, but shi*t happens and it going to end up in your NFT bed.

Heh, not sure what your getting at here

Are you saying sh*t as in, fish waste will end up in there? and if so, what is the issue with that?

or are you saying sh*t as in, stuff from the nft, will end up in the gravel bed?

The plan is to grow duckweed in there to feed the fish.

esobofh,
I actually thing that your proposed layout in that second post of the tread looked nice to me. Even with the bottom of the fish tank below grade, the top of the water should still be above the grow bed top so you could do something like that, just add a sump after the on the ground grow bed and the sump pump could then pump up top whatever NFT or DWC stuff you might want to add later.

Here are a couple points about having the fish tank drain into a gravel filled grow bed. The gravel filled flood and drain grow bed serves 3 main functions that are all necessary in the system.
1-Solids filtration
2-Bio-filteration
3-place for plants

It is good for solids to go into the gravel filled bed as those solids can be beneficial for plants and system maturity. You do not want solids building up in the sump, NFT, or DWC areas as in those locations it just causes problems with getting stinky, using up O2, causing root rot, gunking up the pump, etc. It is generally a good idea to have some sort of solids filter before any NFT or DWC culture and a gravel filled grow bed can do this just fine.

I have an on the ground grow bed that actually has a sump pit as part of it, this might not work for a normal single pump system but it is also an option.

Yep - when I said fish tank at highest level, I was referring to the water level.

If you are only growing duckweed in the raft tank, 'solids' removal wont really be needed. Its more of an extra tank than dwc/nft.

If the fish tank is in a lighted area, and you have high nutrient levels, you can get an algae bloom. If you only have a small amount of nutrients and good water flow, it can be uncovered.