In the saltwater I'm just using a Top Fin HOB filter, rated for 60 gallons. It keeps the water plenty clear!
In the 90, I was using a Fluval 404, but unfortunately the power went out and for some reason burned out the motor. So right now I just have a little HOB on it, but it's keeping the water clear surprisingly and my nitrates aren't TERRIBLE, considering. I'm saving up for a new canister, or maybe even some emperors.