I have a relatively new, cycled, 40 Gallon long, lightly planted tank. I currently have two HOB filters (very old but unused until this tank set up a few months ago,Penguin Biowheels). Their combined flow rate is about 250 gph. But, they aren't really getting the job done. I had to install a power head to get the detritus up from the bottom. I'm thinking of switching to a canister filter. I need it to be small and quiet, as it will have to sit on the table behind or beside the tank. What flow rate should I be aiming for? Any recommendations? I'm looking to keep the cost below $100. Thanks!