I have a 40 gallon long, currently with two HOB biowheel filters totaling 250 GPH. I hate these filters. Every time I try to mod the media, I get too much bypass, and the wheels stop spinning. They don't generate enough suction to get the detritus of the sand. They're noisy, and they cause too much evaporation. I've been thinking about n Aquaclear 70, but I don't understand how water flows through it. So, I worry that water would just stagnate at the bottom, while circulated water flows through the path of least resistance. Am I crazy? I want to switch to a canister filter, but the location makes it impossible to place the canister below the tank. What other options do I have? I'm still a newbie.