Loaches Online Forum

I have my 400 gallon tank setup. I need to buy the pumps to power the closed loop system. The tank is 10ft long. All the water drains from one side using a wall drain and needs to be pumped back to the other side using bulkheads drilled on the other side for the returns. I alrdy have 2- Eheim 2260's plumbed in and a sump system as well.

Whats an ideal GPH for the pumps? I dont want to be blowing the fish away. Id like the flow to be natural like in their natural habitats.

The loaches going in are ~40 clowns, ~8 kubotais, ~8 darios, ~8 yoyos, ~8 striata, ~6 schistura manherti, and ~8 histronicas. I might leave the schistura out and put them in a tank w. some sids. Im pretty sure all these loaches come from similar habitats, please tell me if i'm wrong.

Im probably going to have a few rainbow fish and roselines as dither fish. Maybe another type of barb.

Sounds like a great tank!
I think I would aim at about 10 times the tank volume per hour, if the plumbing can handle it.

The drain wall has 2 - 2" drains

The Return wall has 4 - 1.5" outputs

You can get 1000 gph through 1" pipe, with the right pump, but the limits of your system is that the 2" pipes are gravity fed. At some point the water will not be able to enter those pipes fast enough to keep up with the inlets from the sump.

Having (4) x 1.5" returns will easily allow you all the flow the fish need.
The concern I have is how fast will it flow out of the tank, even with (2) x 2" overflow pipes.

You might do some research on something called a "Standpipe" and see if you can get a better idea of the potential flow rate.

If the 2" holes were right at the bottom of the tank I could see that much water falling (gravity fed) through the pipes. But if the inlets to these pipes are close to the surface then I can see it as the bottleneck to the flow rate.

The 2" holes are on the bottom of the tank. They are setup as a closed loop system w. the 1.5" returns.

I have more 1.5" drains for my sump, seperate.

In that case you will certainly be able to get some really serious water flow going in this tank.