How to Wash Gravel Substrate

Turn off the tank's filters and pumps. You should leave aeration devices running if you intend to leave animals in the tank during the gravel washing.

Remove sensitive animals and plants, plus any decorations, rocks or driftwood which may get in your way or which are small enough to get sucked in by your siphon. Put them in an aerated holding tank filled with water from the aquarium from which they came, unless that water was fouled by a dead animal or the tank was "crashing," meaning the water quality became so poor that animals died. In that case, use new water as close as possible to the water conditions normally in the tank.

Set a net on top of a bucket. Place one end of the siphon in the net to catch gravel as it comes out of the siphon. The bucket catches dirty water which you will discard as it fills.

Start your siphon. A manual siphon which does not require attachment to a sink faucet works best. Begin the flow by sucking on the end of the siphon.

Move the siphon carefully along the gravel, allowing it to suck up the gravel and any debris or waste while being careful of any animals still in the tank. Aquatics Unlimited recommends only taking out about one third of your water at one time. Repeat Step 5 in another week if you are unable to get all the gravel out at once without draining your tank.

Keeping the gravel in the net, rinse the gravel using either water from your fish tank or water in as close condition to the usual water quality of your fish tank as possible. Do not use tap water, which will kill the beneficial bacteria living in your gravel.

Replace the rinsed gravel and fill the tank with new water. Allow filtration to run and debris to settle before returning animals or plants to the tank.