I saw a rule of thumb for this. 4x to 8x the tank size in gallons per hour. So 480 to 960 gph
. Your Cascade 1500 is rated at 400gph.
Does the Cascade bypass some water? Some do when they start to clog. Either that or you dont have a fine enough media to trap the small stuff. Add to that not enough gph
A second filter would be best for this size tank. A model in the 200 to 400 gph
range will do fine.
Etheim, Filstar, Fluval or another Cascade.
Or you could use a HOB
(power filter) instead.
Aquaclear AC300 Maximum Output: 300 U.S. gal
. per hour or the AC500 Maximum Output: 500 U.S. gal
. per hour.
Emperor 400 Flow is 400 GPH
or the 280 Flow is 280 GPH
There seems to be several people that use the canister and hob