To expand on my already long-winded post- you don't need 3 or 4 filters on that tank. I was just saying how much more expensive a single FX5 is than multiple eheims. Honestly, a single 2217 might be enough to eliminate all of the ammonia & nitrite, but I'd worry that it didn't have enough water movement to keep the tank aerated well enough. I think you'd also end up with way too many still spots in the tank with only one on it. Were it my tank, I'd go with two 2217s or two XP3s- they seem to be fairly comparable. I almost bought an xp3, but then I realised that by the time I bought media, the 2217 was cheaper.