I only have to change the water once a year and it’s crystal clear. I run an underground suction biological filter, with an external canister filter pump. I double the life for the canister’s carbon and amonnia removal medium, when I remove a gallon to water the plants. I do it for the plants more than the fish. I of coarse stop using it on plants, when adding treatments for disease. I do a gravel cleaning with the wand attachment for the canister filter pump, every two weeks. Like I said it’s crystal clear.