I've been using AquaClears for years, and I'm running two AquaClear 110's on my 75 gallon right now (because I like to over filter), but one is more than adequate for a 75 gallon. My water is always crystal clear, and my parameters are always stable. With AquaClears you get mechanical, chemical and bilogical filtration. And you can use any type of filter media you choose. IMO - they are the best HOB filter you can buy. And the price is right too - while I was in PetSmart the other day, I noticed that they had them on sale for $67.99 (the 110s normally run at about $90.00).