Standard Community Tank
25-30% weekly. Refill with dechlorinated, temperature-matched water.
Vacuum substrate during change to remove waste accumulation.
Heavily Stocked / Goldfish
30-40% weekly. Goldfish produce massive waste loads.
Some serious goldfish keepers do twice-weekly changes.
Heavily Planted
Less frequent, smaller changes — 20% bi-weekly.
Plants absorb most nitrate naturally. Big changes can disrupt established ecosystem.
Discus / Sensitive Species
Daily 25% changes for serious discus keepers.
Or 50% weekly with ultra-careful water aging and dechlorination.
Reef Tanks
10-15% weekly with marine salt. Trace element replenishment.
Auto top-off (ATO) for evaporation, not for waste removal.