Planted Tank Guru
Join Date: Jan 2010
Location: Contra Costa CA
Larger than 20 gallon box as a sump (Probably- see notes below).
Drill all the tanks.
Have ball valves on each 'in' pipe so you can control the flow into each tank.
Sump pumps can be throttled down with these ball valves so they are returning less water than their maximum capacity. But if you undersize the pump there is no way to make it pump more water.
Here is the water flow pattern:
Out of each tank via the drilled holes. Drill them in the back wall, an inch or two below the water line. Larger tanks can have more holes or larger holes (or both).
Gravity feed to a main waste line, leading to the sump. Discharges over a filter mat that may be a home for nitrifying bacteria, but also stops the coarsest of debris (leaves).
Under this mat is the rest of the filtration, heater, CO2 injection and anything else you want. Baffles are really helpful. Force the water to go up and over then under to make the debris settle out.
Pump returns the water to the tanks. OK if this plumbing goes over the edge of the tanks, add spray bars if needed. It may be plumbed with a larger pipe as it leaves the pump, then reduced as the pipe tees off to each tank, ball valve at each tank, or it can be plumbed through a manifold so all the ball valves are in one place.
All based on class 200 PVC:
10-15 gallon tanks are probably OK with 1/2".
20-30 gallon should have 3/4".
Up to 50 or even 75 gallon 1" would be OK, but it might be a good idea to have 2 or more overflows. (My 125 has 1 @ 1", but also has other filtration. My 72 has 1-1/4")
When you connect 2 smaller pipes together bump it up to a larger pipe size.
Screen the overflows to keep fish out. If you are raising shrimp or fry these screens may be sponges over the intakes, but CLEAN THEM FREQUENTLY. Intakes are at the top of the water. If you want bottom of the tank intakes you need to make sure a power outage will not siphon all the water out of the tank. Some combination of elbows in the 'in' plumbing, inside the tank, will allow you to fine tune the water level.
Unions anywhere you want allow you to take it apart for cleaning the pipes, but I would for sure add a union right after the pump so the pump can be removed for cleaning or to replace it. Other unions are optional.
Here is how to figure sump size:
How much is the maximum amount of water that could flow into the sump if the power cut off?
10 tanks of 20 gallons (1' x 2' surface area) with holes drilled 2" below the water line.
10 x 1' x 2' x 2" = 3.3 cubic feet. x 7.5 gallons in a cubic foot = 25 gallons.
Assume that a safe 'overflow/power out' condition is sump 3/4 full (There is equipment and filter media taking up space in there) means a sump of a minimum sump size pretty close to 35 gallons.
I would sure do a test run to be sure of this, and be ready to get a larger sump if this minimum size is too small.
Another way to reduce the 'power out' water landing in the sump is to put an anti siphon device (simple flapper style) in the discharge line. Add a union so you can disconnect and clean it about once a year (YMMV).
Do a few searches using the term 'fish room' and get more plumbing ideas.