Hello and Welcome to Fish Lore. As for filtration...your filter gallons per hour (
GPH) is recommended to be 8 to 10 x the volume of your tank. For 90g's a 900gph filter would be great. I'm not familiar with the gx6000 I use mag drive pumps.
As for heating, Visi Therm Stealth Heaters are a big hit on this forum. I use them in both my tanks. Very accurate. I'd suggest 2 200w heaters one on each end of the tank. This will help to eliminate cold spots by having 2. Also by having 2, should one quit working for whatever reason you have a back up. Best of luck and keep sending pictures!
