thats a big ol' can of worms. pretty much any type of filtration will work. you will have to do some looking, and see what most appeals to you. there are under gravel filters which are old fashioned, but work. sponge filters , ziss moving bed bio filter, these 3 are powered by air. there are hang on back filters which can take many kinds of media, and sponges, and there are canister filters which can also take all kinds of media and sponges etc. i would find what seems to most appeal to you, then figure out how best to use it. i myself am primarily a hang on back person, but any of the choices can work fine.