Powerheads For Powering Undergravel Filter

[joselito.rd]

I'm setting up a new tank with undergravel filter and I have a question, how much GPH do I need in a 26 gal tank using two powerheads for powering undergravel filter?

 

[TwoTankAmin]

The key to undergravel filters is proper size and depth of gravel and then a nice slower even flow rate. I would suggest you consider running your system as a reverse undergravel system. if you do this you should have a small hang on filter as well to remover mechanical waste (consider an Aquaclear 20). You can get a powerhead reversal kit for just this purpose or buy a powerhead that can run in reverse.
 
I would think PH rated in the 120 gph range would do fine when combined with a 2nd filter. If you don't do the 2nd filter then i would want something closer to a 200 gph flow rate.
 
The advantage to an RUGF is that instead of sucking things down into the substrate, which means a regular gravel vacuuming routine is essential, it blows up through the gravel keeping solid wastes suspended in the water where the 2nd filter, set up for mech. waste, will remove it. Bear in mind that an undergravel system, run properly, is still one of the best bio-filters there is. However, the hang on will handle the mechanical waste and when you need to add some carbon, it also goes in the hang on. The hang on also acts to aerate the water by aggitating the surface.