How to Clean a Fish Tank
Unplug the heater and filter. If using an air pump, unplug and remove the air stone from the water.
Remove large ornaments and plastic plants. Lift slowly as not to stir up the fish waste underneath. Important note – if you have live plants, never remove them as you will disturb root growth.
Rub the inside of the glass with an algae scrubber or clean facecloth. Slow, light circular motion works best. Although the glass is tempered and can resist pressure, you don’t want to challenge the strength by pressing too hard!
Using a gravel siphon, remove 25% of the water into a large bucket. To be more specific, move the siphon end through the gravel in a twisting and circling motion. This will further enhance the vortex sucking up the detritus on the bottom. If the gravel layer is thick, make sure to dig past the top layer retrieving tiny particles that get wedged deep down.
Rinse the filter pad and rub off algae growth on the ornaments inside the bucket of fish water you just removed from the aquarium.
Place filter cartridge/media and ornaments back into the tank and filter respectively.
Empty the fish water bucket and fill the bucket with tap water. Move the thermometer from the aquarium into the bucket and ensure both temperatures are relatively same.
Add water conditioner (follow the instructions on the package). If your aquarium is still in its cycling period (first 3-4 months), add living bacteria supplement too.
Fill the aquarium back up slowly. A water jug is preferred to fill up the aquarium than lifting the whole bucket and it helps prevent spills as well.
Plug in the heater and filter and re-arrange the ornaments if any. Keep the lights off for a few hours, darkness is calming for your aquatic inhabitants as they adjust from the stress of the water change.