A 10-gallon aquarium needs a partial water change and filter cleaning every one to two weeks, and a full substrate cleaning once a month

A 10-gallon tank is small enough that waste builds up faster than in larger tanks, so regular cleaning keeps your fish healthy. The process has three parts: removing and replacing some of the water, cleaning the filter, and vacuuming the gravel or sand on the bottom. You do not need to remove your fish or drain the tank completely for routine maintenance—in fact, doing so stresses them and removes the beneficial bacteria that keep the water safe.

The whole job takes 20 to 30 minutes once a week, plus a deeper gravel cleaning once a month. You will need a bucket (dedicated to the tank, not one used for cleaning chemicals), a siphon or aquarium vacuum, a soft brush or sponge, and dechlorinated water at the same temperature as the tank water.

Key Takeaways

  • Change 25 to 30 percent of the water every one to two weeks by siphoning it out and replacing it with dechlorinated water of the same temperature.
  • Clean the filter media (sponge, cartridge, or floss) in old tank water you have just removed, never in tap water, because tap water kills the bacteria that process fish waste.
  • Vacuum the gravel during water changes by pushing the siphon tube into the substrate and letting gravity pull debris into your bucket.
  • Wipe the inside glass with a soft sponge or algae scraper, but avoid any cleaning products—plain water is all you need.
  • Never clean the filter and do a full gravel vacuum on the same day; alternate them to keep beneficial bacteria stable.

How to siphon water out safely

A siphon is the fastest way to remove water and is gentler on fish than a net or cup. Fill the siphon tube with water first (either by submerging it in the tank or filling it by hand), then place one end in the tank and the other into your bucket on the floor. The water will flow downhill into the bucket once the siphon starts. You can buy an aquarium siphon at any pet store for $10 to $20, or use a length of clear tubing if you already have one.

Remove about 25 to 30 percent of the tank's water—for a 10-gallon tank, that is roughly 2.5 to 3 gallons. Do this slowly so you do not stir up the gravel and cloud the water. If you have fish that hide or are easily stressed, dim the lights or do the cleaning when they are less active.

Cleaning the filter without killing beneficial bacteria

The filter is where the bacteria live that convert ammonia and nitrite into less toxic nitrate. If you rinse the filter in tap water, the chlorine kills those bacteria and you have to wait weeks for them to regrow. Instead, rinse the filter media in the old tank water you just removed—it is already in your bucket.

Squeeze or swish the sponge, cartridge, or floss gently in the old water until it stops releasing debris. If the filter is very clogged, you can rinse it a second time in fresh old tank water. Do not scrub it hard or wring it out. Once it is clean enough, put it back in the filter. If your filter has a mechanical stage (foam or floss) and a biological stage (sponge or media), clean only the mechanical stage each week and clean the biological stage every two to three weeks.

Vacuuming the gravel during water changes

Uneaten food and fish waste settle into the gravel and create pockets of ammonia. An aquarium vacuum (also called a gravel vac) is a tube with a wider chamber at the top that you push into the gravel; as water flows down the tube into your bucket, it pulls debris up with it. You can buy one for $15 to $30, or make a straightforward version by attaching a wider tube to the end of your siphon.

Push the vacuum tube gently into the gravel in one spot for a few seconds, then move to another area. Work your way around the tank, but do not vacuum the entire substrate every week—that removes too many beneficial bacteria. Instead, vacuum half the gravel one week and the other half the next week. Once a month, you can do a full gravel cleaning if the tank looks very dirty.

Replacing the water at the right temperature

Before you add new water, check its temperature with a thermometer. Water that is too cold or too hot stresses fish and can cause them to stop eating or become sick. Let tap water sit in a bucket for 24 hours so it reaches room temperature, or use a thermometer to match it to your tank. Most tropical fish tanks should stay between 76 and 80 degrees Fahrenheit.

Add dechlorinated water slowly, pouring it gently into the tank or over a plate or rock so it does not blast the gravel and cloud the water. If you use a water conditioner, follow the bottle's instructions for how much to add. Some conditioners remove chlorine when ready, while others need a few minutes. Once the water level is back to where it started, you are done with the water change.

Cleaning the glass and decorations

Algae grows on the glass and can block your view of the fish. Use a soft sponge, cloth, or algae scraper (a plastic or magnetic tool made for aquariums) to wipe the inside glass. Do not use any cleaning products, vinegar, or soap—they are toxic to fish even in tiny amounts. Plain water and a soft sponge are all you need.

If you have decorations, rocks, or plants, wipe them gently with a soft brush or cloth during the water change. Do not remove them unless they are visibly covered in algae or debris. Decorations also harbor beneficial bacteria, so leaving them in place helps keep the tank stable.

What to do if the water turns cloudy

Cloudy water usually means a bacterial bloom—a sudden spike in free-floating bacteria—which happens after you clean the filter or do a large water change. This is not dangerous and will clear on its own in a few days. Do not do another water change or clean the filter again; just let the tank settle. If the water is still cloudy after a week, check that the filter is running and that you are not overfeeding the fish.

If the water smells bad or the fish are gasping at the surface, the tank may have a more serious problem like ammonia buildup. In that case, do a 50 percent water change when ready and check that the filter is working. If the problem continues, the tank may be overstocked or the filter may be too small for the number of fish.

Frequently Asked Questions

How often should I clean a 10-gallon tank?

Do a partial water change and filter cleaning every one to two weeks. Vacuum half the gravel each week, alternating sides. Once a month, do a full gravel cleaning if the tank looks dirty. The exact schedule depends on how many fish you have and how much they eat—more fish means more waste and more frequent cleaning.

Can I use tap water straight from the faucet?

No. Tap water contains chlorine and sometimes chloramine, which are toxic to fish and kill beneficial bacteria. Use a water conditioner to remove these chemicals, or let tap water sit in an open bucket for 24 hours so the chlorine evaporates. Some areas have very high chlorine levels and require a conditioner even after sitting.

What if I clean the filter and the water gets cloudy?

Cloudiness after a filter cleaning is usually a bacterial bloom and is not harmful. Do not clean the filter again or do another water change—just wait a few days for it to clear. If you clean the filter too often, you remove too many beneficial bacteria and the tank becomes unstable.

Do I need to remove the fish during cleaning?

No. Removing fish stresses them and removes them from the beneficial bacteria in the tank. Leave them in while you do a partial water change and filter cleaning. Only remove fish if you are doing a full tank drain, which should be rare—usually only if the tank has a serious problem or you are moving it.

How do I know if my filter is too dirty to work?

If the water flow from the filter outlet slows down or stops, the filter media is clogged. Clean it in old tank water as described above. If cleaning does not restore the flow, the filter media may be worn out and need to be replaced—check your filter's manual for the correct replacement cartridge or sponge.