If possible, avoid adding untreated water straight to the aquarium. If you have to do this, let the water run for 5 minutes before filling your bucket or tank. Try to use the same buckets for every water change to minimize the risk of transferring harmful foreign bacteria into the tank. The conditioner will neutralize dangerous chemicals, metallic residue, and chlorine in your tap water to make it safe for your fish.

Leave your fish in the tank while you perform the water change. Removing them will probably stress them out even more. Heaters and filters may overheat and crack if they’re running without enough water coverage.

Rub the debris off or let the decorations and plants sit in an natural aquarium cleaning solution. Do not use soap to wash off decorations. The chemical residue can harm your fish or encourage an algae bloom. If needed, use tank water to rinse. Leave live plants in the tank. Uprooting them might kill them or hinder their growth.

Work slowly and gently, taking care not to bump, touch, or stress out your delicate fish.

Use your net again to scoop any floating particles that get stirred up by the siphon. Move slowly and mindfully around the tank to avoid frightening your fish too much. The debris will be organic matter like leftover food, fish waste, or algae.

Never remove all of your tank’s water at once unless there’s an emergency. Too much new water ruins your tank’s chemistry and shocks your fish. At most, remove 50% of the tank’s water (especially if you change the water infrequently). Try using an automatic or battery operated siphon. If possible, avoid using the reverse feature that adds tap water directly to the tank. [8] X Research source

Never use soap or tap water on your filter media. It will kill the helpful bacteria and alter the tank’s water chemistry once you put them back in. Only replace the filter media if they’re starting to fall apart. This keeps the bacteria levels in your tank stable over long periods of time. Keep the sponges in the bucket of tank water until you’re ready to plug the filter back in. If they dry up, the bacteria may die.

Use an aquarium test kit to check the pH levels of the tank and bucket. Most freshwater fish thrive in a pH level between 6. 8 and 7. 8 (neutral). Adjust the pH of the bucket to match the tank water. Add peat moss to lower pH (more acidic) or baking soda to raise pH (more basic). Wait at least several minutes for the pH level to shift before adding the water to the tank.

Try scooping up the new water with a clean pitcher if the bucket is too unwieldy to handle. Fill until you’ve fully replenished the tank and the water level is high enough for the heater and filter to work correctly.

Leave your tank lights off for a while after your water change. Your fish will be startled by the commotion and the lights can add extra stress. [14] X Research source

Dump dirty tank water in the tub or sink, in your grass, or use it to water plants. Store your equipment in a designated spot for aquarium supplies to keep everything handy and in good condition.

Do an extra water change after big changes or emergencies in your tank like new decorations, a chemical imbalance, or a virus or fungal infection.

Anything that’s not eaten after 4-5 minutes will probably never get eaten and become debris on the bottom of your tank. Much of the debris that you siphon out of the gravel will be leftover food. [21] X Expert Source Doug LudemannAquarium Care Professional Expert Interview. 27 August 2019.