1 canister for 5 20g tanks

[Fivepnt0]

Wondering if anyone uses 1 Canister for more than 1 tank and what is the best approach. Im thinking overflow boxes or simple inline valves to control intake and discharge.

[Apistomaster]

I haven't tried what you are comtemplating but my experience with centralized systems has led to my conclusion that a large wet/dry filter would be the better system. Most canisters, even that larger ones really don't have pumps capable of handling high head pressures. In their normal set up the intake and returns are at the same level so head pressures are low. With a wet/dry filter it is easy to select a pump with enough power to over come head pressure and even with the separate return flows each tank would receive a good flow if the pump is sized properly. There are some large canister filters like Ocean Clear that do have the ability to use the pump of your choice that would work in your proposed filter system. Passive overflows are the safest way to handle tank effluent since is is very difficult to construct a balance closed system using multiple valve which are prone to biofilm build up making balancing the flows a nightmare.
If these tanks are for discus an alternate system that works well for me and probably was cheaper to set up was to use two large pedestal sponge filters per tank. One is air driven and the other is powered by an MaxJet 600 power head. I clean only one sponge at a time to retain biological filteration. The power head effluent is deflected up toward the surface so the discus have a good flow but not a strong current to fight. It has allowed for considerable carrying capacities in the 20H and 20L tanks but this is also used on tanks up to 50 gallons. Since these are rearing tanks with many fish and heavy feeding I try to change at least 2/3 of the water every other day. Some require that much everyday because of the bioload.

[Fivepnt0]

Thanks for your input. think im going to do the powerhead connection, maybe a reverse flow......

[Cosmo]

I'd have to agree fully with Apistomaster. I wouldn't run a reverse flow powerhead through the sponge. Directing the output upwards not only reduced turbulence in the tank but also promotes oxygen exchange by creating turbulence on the surface.

Jim