Water changes, feeding and filter care condensed into a calm 20-minute weekly habit.
By Wu Fang · 2026-08-28
An aquarium is a closed loop that slowly concentrates everything you add: food becomes waste, waste becomes nitrate, evaporation leaves minerals behind. Maintenance is the export side of that loop, and it works best as a calm weekly habit rather than a monthly rescue mission.
A consistent 25% weekly water change removes roughly a quarter of the accumulated nitrate each week, keeping the tank in a stable band. Skipping four weeks and then changing 80% shocks fish with a sudden chemistry shift — the very thing stable tanks avoid.
Work in the same order every week so nothing is forgotten. Siphon the substrate while removing water — debris trapped in the gravel is the single biggest source of nitrate and hydrogen sulfide pockets.
Match the new water to the tank: same temperature within 1–2 °C, dechlorinated, and if your tap GH/KH differs sharply from tank water, pre-mix and aerate it before adding.
The filter media holds your nitrogen-cycle bacteria, so treat it as living tissue. Mechanical prefilter sponges need rinsing every week or two; biological media needs rinsing only when flow visibly drops, and never more than half of it at once.
Rinse everything in water removed from the tank — never tap water, whose chlorine is designed to kill exactly the organisms you are keeping. Replace cartridges and floss on a staggered schedule: one third of the media each month, never all at once.
Feeding is the input side of the loop. One or two small meals a day — eaten within two minutes — keeps inputs low enough for your routine to handle. A fasting day per week is genuinely beneficial for most community fish.
Watch body condition rather than the clock: slightly rounded bellies on juveniles, lean but not hollow profiles on adults. Adjust by observation, and remove any uneaten food within five minutes.
25% weekly suits most stocked community tanks and keeps nitrate under 40 ppm. Heavily stocked or lightly planted tanks may need 30–40%; heavily planted, lightly stocked tanks can stretch to every two weeks. Test nitrate — it is the only honest answer to this question.
Yes. Changing more than 50% at once risks shocking fish with shifts in temperature, pH and GH, especially if your tap water differs from the tank. In an emergency (ammonia spike, medication overdose) large changes are correct — otherwise stay at 25–40% per change.
Rinse media gently in water you just removed from the tank, keep it submerged the whole time, and never replace more than half the media at once. If the filter has been off for more than an hour, treat it as an emergency: rinse nothing, restart it, and test ammonia daily for a week.
Yes in bare or sparsely planted tanks, where debris works deep into the substrate. In densely planted tanks with soil substrates, vacuum only the open areas and the top few millimetres — deep, aggressive gravel washing strips nutrients plant roots depend on.
For almost all municipal supplies, yes. Chlorine and especially chloramine are toxic to fish and lethal to filter bacteria, and chloramine does not fully gas off with aging. A standard sodium-thiosulfate conditioner neutralises both in seconds; dose for the full volume you are adding.