How to Clean a Fish Tank

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When buying and assembling your first aquarium, your biggest concerns are likely about the number of fish you can include, the decorations you can buy, and the best lighting you can equip your pretty new tank with.

However, once all these fun tasks are completed, you’ll be left with one, very key question: How do you clean the darn thing?

how to clean a used fish tank

While cleaning and maintenance can be shockingly simple on some tanks, for others, it’s quite a daunting feat.

No matter your unique circumstances, or experience levels, we’re here to give you the long and short of how to guarantee your tank is as pristine and healthy as it can be.

Basic Maintenance Guidelines

To start:

Be sure to feed your fish twice a day and to remove any uneaten food particles. This is to prevent the uneaten food from affecting the water quality in any way.

Check the water temperature and specific gravity of the water daily.

Perform weekly pH, nitrate, nitrite and ammonia level, and (in the case of saltwater tanks) salinity checks.

You can choose to test your water at your local fish store, or buy a do-it-yourself testing kit. These kits consist of a color-coded strip of paper that can help you determine each of the current levels in your aquarium.

You should give your fish tanks a partial water change regularly as well. For freshwater tanks, you should change 10-20 percent of the water every 2-3 weeks.

For saltwater tanks, you should change 10 percent of the water weekly for a year. After that, you can follow the same water change rules as freshwater tanks.

Full water changes should never be needed if you maintain the upkeep of your tank. By doing this, you will remove important bacteria in the water that is essential in breaking down the waste your fish emits, resulting in you having to clean out your tanks or filters much more often.

Keep an eye on your fish and their tank for the initial few months you own them, keeping a record of all the normal parameters the tank should have.

These parameters will differ based on what type of fish you have, so be sure to thoroughly research the conditions your fish normally live in before putting them in the tank.

Whether you have a new or used fish tank, you must never wash it with any kind of soap or detergent, as these will kill your fish. It is difficult to completely remove soap after washing something, and even the tiniest trace can prove lethal to your pets.

But how do you clean a fish tank? It actually differs depending on what type of tank you use.

Below are a few simple guides on the best ways to clean a fish tank.

How to Clean a Small Fish Tank

You may assume that a smaller fish tank is much easier to clean than a larger one. However, while you may have less surface area to cover, larger tanks are actually much easier to maintain.

You should change portions of the water more frequently with a smaller tank due to the water becoming unstable with the build-up of bio-load. The same goes for larger tanks with a lot of fish.

You may also have to remove your fish from this smaller tank each time you clean, which can cause them stress and make them sick.

Leave them in their tank as you clean it as much as possible. If you must remove them, place them in a large enough glass filled with old water from their tank to make them comfortable while you clean.

best way to clean a fish tank


  • Algae pad or scraper.
  • Razor blade (optional).
  • Clean, soft-bristled toothbrush.
  • Bleach (optional).
  • Water siphon.
  • Vinegar or aquarium cleaners.
  • Glass cleaner/lime remover (optional).
  • Filter media and brush.
  • New bucket or bucket used for cleaning aquariums only.
  • Towels.
  • Prepared water (for refilling).
  • Water testing kit.

Cleaning Process


First, unplug anything electrical you have connected to your aquarium, including the heater, the filter, and any pumps you have.

Remove any of the tank’s bigger rocks (not gravel) and other decorations to be cleaned separately.

If you have artificial plants, you can remove them if they need to be cleaned, but do not ever remove live plants, as this will disturb their root growth in the tank.

Algae Removal and Decoration Clean-Up

Use an algae pad or scraper from a pet shop to clean the inside glass of your aquarium and all decorations that have significant algae growth.

Algae pads and scrapers from houseware departments in regular stores tend to have soap or other harmful chemical residues that will hurt your fish. Take care with acrylic fish tanks, as even algae pads from pet stores may scratch them.

You may also use a soft-bristled toothbrush to scrub your larger decorations.

For especially tough residue left on the inside glass, use a razor blade to scrape it off. For acrylic fish tanks, use a plastic blade.

You do not have to wait until your regular tank cleanings or water changes to remove algae from your tank, especially if you want to keep your aquarium nice and clean-looking.

Before you place any rocks or other bigger decorations back inside your fish tank, make sure you wash them all off with warm water beforehand.

Use a 10-percent bleach solution for especially grimy and stubborn decorations and only when necessary.

Be sure to only soak these decorations for fifteen minutes. Scrub any remaining residue off, rinse well under running water, and air dry them to eliminate any remaining bleach.

Siphon the Water and Clean the Gravel

You can use a water siphon to clean any gravel you put into your fish tank. This siphon will suck up small amounts of gravel and water and, depending on the type of siphon you use, the water you collect can either be dumped in a bucket or connect directly to your sink.

This siphon sucks up the debris at the bottom of the tank, which mostly consists of fish waste, and will travel through the water you suck out into either your bucket or sink.

Clean your gravel until you have drained a third of your tank’s water at most. If you want to control the flow of water and debris, you can simply use your thumb to block the end of the tube.

Be sure none of the gravel gets sucked up into the tube that leads to your bucket or sink. Instead, you need to let it settle back in place after cleaning.

Some siphons do have built-in regulators to control the flow of water, too. Be sure to choose the siphon you feel is easiest to use.

Clean the Outer Glass and Fixtures

Vinegar and/or cleaners designed specifically for aquariums are highly recommended as long as you rinse the tank constantly after.

If you must use glass or lime remover, be sure to save it for outside glass and fixtures only! These removers contain ammonia, which is toxic for fish.

how to clean a small fish tank

Clean the Filter Two Weeks Later

By waiting about two weeks after the initial session to clean your filter, you also allow all the good bacteria you have disturbed to settle, too.

These bacteria eliminate the harmful chemicals that can build up over time in your tank. Please note that you should never run your filters under tap water, as this would also remove these good bacteria.

Sponge filters are the most common type of filter. You should remove it and rinse it out in the bucket of water that you have removed from the tank, should you have any to clean it. Mechanical filters should also be rinsed and returned as quickly as possible.

If your filter contains carbon, ammonia absorbers, or ion-exchange resins, you will need to replace it every couple of weeks or so.

Clean the rest of the filter, including the tubing, with a filter brush.

Replace the Water

Whether you have freshwater or saltwater fish, you should always make sure that the water you are replacing is roughly the same temperature and salinity as the rest of the tank water.

A Note on Fish Bowls

You can clean fish bowls in much the same way, although please note that you must clean fish bowls much more often than tanks, especially if they do not have a filter.

Be sure that you change only 10 to 15 percent the water at a time as well. You will also have to remove your fish while you clean the bowl since it is extremely small.

How to Clean a Used Fish Tank

Be sure the tank is completely empty before you begin cleaning. This means dumping out any old water, taking out any old decorations, and temporarily taking out any fish, if there are still any in there.


The cleaning tools you use for cleaning a new fish tank are pretty much the same. However, you will also need salt to clean out the used tank.

You may also need aquarium sealant if this used tank has any cracks.

Cleaning Process

You should follow the first two steps from above, as well as the “cleaning outside glass and fixtures” step, as these processes are performed the same way.

Again, always use algae pads and new cleaning materials that you will use only for cleaning aquariums. Do not mix these with soap or detergent at all.

Scrub the Inside Thoroughly

Scrub the inside glass with vinegar and salt, as vinegar is good at removing hard water stains and getting rid of old fishy odors, while salt is helpful for scrubbing.

Rinse it very thoroughly to get rid of all the vinegar and salt when you are done.

Check for Leaks

Fill up your clean tank with water to check for any leakage.

If you find any, you can use aquarium sealant to patch it up again. Be sure to follow the instructions on the sealant carefully.

Cycle Your Tank

Cycling is simply the process of building up good bacteria within your filter that will convert the more harmful chemicals, like ammonia and nitrite, into nitrate, which is much less harmful to fish and can be easily removed.

Here’s a video showing an example of how to clean a fish tank.

What do you think is the best way to clean a fish tank?

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