Canisters confuse me, and I'm not sure if what ones are best.If you use a sponge filter in a larger tank like a 125g, may I suggest to get one with a coarse foam for more flow.
The "Pro" version of the ATI Hydro Max sponge filters use a coarse foam sponge.
Their larger Hydro Max "IV" or "V" would work well. ATI's are modular, so you can stack one on top of the first.
For example in our 55 gallon African tank, in one corner we have a Hydro Max Pro III (coarse foam) , then a HM II (fine foam) stacked on top.
With a quality airstone and one output of a Fluval Q1 air pump, I get a lot of flow through it.
The only other brand of sponge filter I can recommend is from Swisstropicals.com.
Also, may I ask why not consider a canister filter for such a large tank?
Canisters confuse me, and I'm not sure if what ones are best.
Well, you've come to the right place to ask. I have to admit when I saw you were talking a 125 my first thought was, "Why HOBs?"Canisters confuse me, and I'm not sure if what ones are best.