Should You Vacuum Your Aquarium Gravel?

Vacuuming an Aquarium

Elva Etienne / Getty Images

Aquarium maintenance varies based on your setup, equipment and time. One of these key procedures is vacuuming your substrate, using a gravel siphon. There is some debate as to this procedure is necessary and could possibly making your water quality worse. No matter your setup, vacuuming makes your tank a healthier environment for your fish.

What Is "Vacuuming?"

If this is a foreign concept for you, don't worry; you are not alone. Vacuuming an aquarium is performed using a gravel siphon. This siphon is made up of a large, rigid tube connected to narrower, flexible aquarium tubing. There are some that will hook up to a sink to assist with siphoning, otherwise, you will need the assistance of gravity.

Some vacuums come with an air-filled bladder to start the pull of gravity. Others you will need to start the siphon manually. It is not recommended to suck on the open end of the siphon! Although rare, there are a few zoonotic diseases you can catch from your fish, not to mention getting water in your lungs.

Once your siphon is started, vacuuming is a simple process. If your substrate is too deep (> two inches), vacuuming may not be sufficient to clean the deep layers. Stick the rigid tube into the substrate and allow a few seconds for the sand/gravel/rocks to be pulled into the tube. Before they get more than halfway to three quarters into the siphon, pick up the tube and allow the substrate to fall back down. You will see the lighter particulates, mostly fish/plant waste and excess food, floating up the siphon and into the flexible tubing. Repeat throughout your substrate.

What Does "Vacuuming" Do?

Vacuuming removes the small particulates from the substrate. Mostly, this is made up of fish waste, dead plant material and excess food, especially if you feed a flake diet. These lighter particulates get sucked away while your substrate stays in place.

If those particulates were left in place, it will cause problems with your water quality. Leftover food, fish and plant waste break down and release ammonia into your water. Ammonia is toxic to fish and why you work so hard to cultivate good bacteria in your biological filters. By removing these particulates before they break down, you will decrease the ammonia concentration in your aquarium.

Deep pockets of debris, once cut off from oxygen in the water, can develop anaerobic bacteria populations. These bacteria use sulfur as a food source, and when disturbed, release hydrogen sulfide into the water. This is another toxic substance that can kill fish and cause increased disease. You will know if you have accidentally disturbed these bacteria since your tank will smell like rotting eggs. If this happens, evacuate your fish to clean, treated water as soon as possible and thoroughly rinse your aquarium before putting your fish back.

But if I vacuum, I'll Remove Those Good Bacteria

The particulates you vacuum up are small, but not microscopic. Your good bacteria live in your substrate deep within the crevices. Vacuuming will remove only a tiny percentage. If you are relying on your substrate to do the bulk of your biological filtration for your nitrogen cycle, your system is not sustainable.

All tanks must have biological filter media to colonize good bacteria. Be they sponges, matting, fluidized beds, socks, bioballs or rocks, there are many ways to house good bacteria in fish tanks. Vacuuming your substrate as part of your regular maintenance will not significantly diminish your bacterial colonies.

What About Planted Tanks?

These systems may be less well tolerant of vacuuming. Plant roots can become dense and make vacuuming almost impossible. For these systems, it is critical that the roots get oxygen and don't create those anaerobic colonies we mentioned earlier. It is recommended you use a substrate specific for plants.

What if I Don't Have a Vacuum?

If you do not have a vacuum, you must have another way of removing fish waste and plant material from your tank. Undergravel filters are a tricky business and should not be used as a complete maintenance replacement. In fish tanks with only a few fish, some owners remove waste with a simple turkey baster. Scavenger species, such as shrimp and snails, can break down the waste organically, but only in tanks with low fish density.

You must also be very careful when feeding to make sure there is no excess food wasted. This is easier when using a pelleted food over a flake food. Pelleted foods pack more nutrition overall and come in very small sizes.

How Often Should I Vacuum My Tank?

As with all best maintenance routines, regular vacuuming, either once a week or once every other week is best for your aquarium. Be sure to remove all your decor prior to vacuuming. You'll be amazed how much waste settles under those pretty plants and castles.

Vacuuming provides a quick and easy way to perform your regular water changes. Use the waste water for your plants or gardens!

Overall, vacuuming is an easy way to keep your aquarium healthy and will not decrease your biological filtration.