First Tank Guide Tank Logo
First Tank Guide Home

Cleaning Your Aquarium

Performing Your Weekly 10-15% Water Change

(The First Tank Guide)

For all of you who have asked about cleaning fish tanks... Cleaning your aquarium is a simple and straight forward task, and should not take very long (Unless you have a particularly small tank or bowl, in which case care can be quite cumbersome and time consuming). The better care you provide for your tank, the healthier your fish will be, the nicer your tank will look and the easier your tank will be to care for in the future.

Don't I Have to Remove Everything from the Fish Tank when Cleaning?

You should not need to take all the stuff (plants, decorations, etc.) out of the fish tank when you clean it. In fact, I would not recommend it. This just produces extra work for you and creates a large and unnecessary mess. Remember, every surface in the tank will grow some beneficial bacteria that are part of the biological filter. By removing and cleaning the decorations you stress (and may even kill) some of this bacteria, reducing the quality of your filtration until the filter recovers.

What About Removing the Fish when Cleaning the Aquarium?

Similarly, you do not want to remove the fish from the tank when you do your regular 10-15% water change. This, again, is a lot more work on you, and creates an unnecessary mess. In addition, this can be highly stressful to the fish, and is likely to cause physical injuries to your fish.

OK, So How Do I Clean My Fish Tank?

When cleaning your aquarium, you should just remove part (10-15%) of the water and replace it with fresh, dechlorinated tap water (bowls and vases require larger water changes more often). While you are doing this, you should use your siphon to suck up some of the gunk that collects in the gravel and decorations. If you have an under gravel filter, it is very important to clean the gravel when you do your weekly water changes, this will prevent detritus and other decaying organic matter from blocking the passages between the pebbles and restricting water flow. Generally, you can clean 25-33% (1/4-1/3) of the gravel while siphoning out 10-15% of the water.

What About Algae?

If you have algae growing on the surface of the tank or ornaments, you should get an algae scraper of some sort and scrub the glass before removing water. Many varieties of algae scrapers or scrubbers are available at your local pet store. For additional cleanliness, you could get algae eating catfish and/or scavengers to pick up some of this work for you, however, having catfish in the tank does NOT mean that you don't need to clean. In fact, algae eaters and catfish, like any other fish, will add to the biological load of your tank and increase maintenance requirements. (And even those catfish that will eat some algae will not eat much and are unlikely to keep the tank looking clean.)

Catfish or no catfish, I recommend doing 10-15% water changes once a week for the life of your aquarium. Once you get into this habit, it is not really that much work. Really, it isn't that much work. Cleaning all the fish tanks in a local pet shop was only a 3 hour job. Doing your weekly water change in your own home aquarium should not take too long.

What If My Filter Is Dirty?

If you have to clean out the filter(s) do not change all the media (cartridges, sponges, carbon packets, etc.) at once, as this will remove the majority of your biological filter, causing the tank to have to go through a cycling period again to get bacteria reestablished. Rinse any new filter media in cool running water before introducing it to the system (unless the instructions for the filter media specifically state not to).

OK, I Have the Old Water Out, Now What?

Once you have siphoned 10-15% of the water from your tank, you will need to fill it again. The easiest and neatest way to do this, is to use a siphon to siphon water from a bucket into the tank. This will tend to reduce spilling and messing up the gravel and decorations. Use a bucket that has never had detergents or household chemicals in it (I recommend getting a bucket specifically for use for aquarium chores) and fill it with water. The water should be close to the temperature of the tank water that you just took out (the average person can tell temperature differences within 1/2 degree Fahrenheit or about 1/4 degree Celsius with their hand, so just feel the water to see if it is the same). Use a chlorine or chloramine remover to prepare the water for introduction into the tank. Place the bucket somewhere higher than the top of the fish tank, and get your siphon going again and in just a couple of minutes, you should have a full tank. Be sure to watch the siphon, in case the hose gets bumped out of the tank, or if there is enough water in your bucket to overfill the tank. Remember, there needs to be some space between the top of the water and the aquarium cover, because your fish rely on oxygen exchange at the surface of the water in order to be able to breathe.

What About Topping Off the Fish Tank Between Water Changes?

Do not just "top off the tank" to replace water that "disappears." This water that is disappearing is evaporating, and it leaves behind all the impurities that were in it to begin with. This means that as you just top off the tank, you are making your water harder until it will eventually no longer be able to support fish.

Additionally, if there are even trace amounts of heavy metals or other toxic substances in the water, you are giving your fish more and more of these every time you top off the tank. Most municipal water systems have at trace levels of at least one potentially hazardous substance, but in minuscule amounts these should never be trouble for you or your fish. Furthermore, by not removing water from the tank from time to time, you allow build up of waste products not removed by the filter (such as Nitrate), which are potentially hazardous to the fish and encourage algae growth.

Usually, if there is significant evaporation between water changes, you are either going far too long between water changes, or there is something wrong with the aquarium setup or equipment that is causing or encouraging evaporation.

Aquarium Cleaning: The Short Version

Remember, cleaning your tank is easy. Scrub for algae, remove 10-15% of the water while cleaning the gravel and top off the tank with dechlorinated water.

These cleaning tips are intended for tanks that are already cycled and are over about 10 gallons in size. Care requirements may vary for tanks that are still cycling or for small aquariums and fish bowls.

"Thanks for the excellent web site."
March 2, 2003
More Comments
"I would like to say your website has been the most informative of all...I have not had problems following your advice."
April 27, 2012
More Comments