Having a beautiful home aquarium is fun and exciting. To keep it awesome looking, you have some regular aquarium maintenance work to do. In other words, you must know how to clean a fish tank. 

An aquarium is not something you can just set it up once and enjoy it without taking care of it. Harmful chemicals can build up in the fish tank over time.  Water PH might crush.  Algae and carbon deposit, as well as some organic materials, can build up on the glass of your fish tank.  More and more fish poop can become visible on the substrate. It requires your regular attention to keep the fish as well as the whole aquarium system healthy and beautiful.

To keep the fish and the aquarium system healthy, we recommend weekly aquarium maintenance. Although you may do it once every two weeks, weekly maintenance keeps the aquarium and fish healthier. In fact, it makes your job easier if you do it more frequently.

I. List of tasks during aquarium maintenance and the reasons to do them

1. To do a partial water change of 30~50%
Sure, everyone knows that we must change the aquarium water at some point. What some people might not know is why we must replace the aquarium water.  And how much water to replace.

If you have a good understanding of Aquarium Nitrogen Cycle, you should know that nitrate will build up over time. While nitrate is relatively harmless, it can affect the fish’s immune system in a long run when the concentration is too high. Typical aquarium hobbyists aim for below 40ppm for nitrate concentration in the fish tank. The only way to remove nitrate is through partial water change. For more sensitive fish, below 20ppm might be ideal. The lower is better, aim for 0 but do not get stressed over anything in the 20~40ppm range.

The process of forming nitrate is also acidic.  It can eat away at the water buffer over time.  As a result, at some point, it will eventually crush the water PH.  In this case, the water PH can suddenly go from 8.0 to 5.0 or even lower. It is incredibly unhealthy for the fish to experience such a sudden massive swing in water PH. In fact, any significant change in the water perimeter such as water temperature, PH, hardness, and nitrate concentration all can shock and even kill the fish.

It is precisely why we recommend partial water change instead of full water change. In fact, never do a full (or 100%) water change.  Never take the fish out of the tank during the water change for the very same reason of not to shock them. Weekly instead of monthly water change is also for the same purpose because if you wait for too long before a water change, there will be more nitrate and the PH might be too low. Then a sudden water change will restore the PH, and it can also shock the fish.

The percentage of partial water change is not a fixed number. You may change as little as 5~15% or as high as 70~90%. The idea is to replace just enough water to keep the harmful substances in the water in check without shocking the fish. Therefore we recommend 30~50% as a standard. You may choose any percentage according to your own need. Heavily stocked aquarium’s nitrate level naturally builds up faster, thus requiring a more significant portion and more frequent water change.

2. To clean the substrate for debris
It is obvious that fish will produce waste. Fish poop is not a pretty sight, especially when there is a lot of it at the bottom of the tank. The insightful scene is the least of your worry. While a bit of fish poop should not be your concern, too much fish poop builds up over weeks and months, and it might set the aquarium nitrogen cycle off balance, causing an ammonia spike. Even if the aquarium filter is efficient enough to avoid an ammonia spike in your aquarium, nitrate will still build up much faster.  Because there is a higher production of ammonia. It can result in so-called Old Tank Syndrome.

As was mentioned in Aquarium Filter For Fish Tanks, to remove the fish poop, you will need to use an aquarium vacuum to suck up all the fish waste and other debris from the bottom of the fish tank during every partial water change.

3. To clean the sides of the fish tank
It is not uncommon that there will be build-up on the sides of the fish tank glass. Sometimes it can be algae; sometimes it can be carbon deposits and even some organic material produced by the breakdown of fish poop and leftover fish food. Whatever it is building up there, it can make the aquarium look dirty, thus blocking your view. Regular cleaning will ensure crystal clear glass for your enjoyment.  You can quickly do it with a piece of algae scraper.

4. To clean the aquarium filter system
It is natural for some debris in the fish tank such as fish poop and leftover fish food to get sucked up into the aquarium filter, and the water flow rate of the filter will decrease over time. Too much debris in the filter system over an extended period (usually months) can put too much strain on the filter’s little motor. You might hear the filter getting louder and louder. In some extreme cases, it can damage the motor and cause malfunction to the filter system.

While it is not recommended to clean the aquarium filter too often to avoid possible damage to the beneficial nitrogen cycle bacteria colonies in it, the filter system still must be cleaned once in a while to keep the water flowing.  And to avoid an old tank syndrome resulting from too much fish poop and other organic debris building up inside the filter.

How often the aquarium filter needs to be cleaned depends on what type of filter system you have. For example, hang on the back power filter might require more regular maintenance than a canister filter because it usually can suck in more debris. It is recommended that an aquarium filter system should be cleaned at least once a month.
It also depends on how well the filter itself is protected. If you have a pre-filter installed on the intake of your filter system to block the debris from getting in, you might not need to clean the filter for months. In this case, you will need to regularly wash the debris off the pre-filter, which is much simpler than cleaning the filter itself.

Now we know why the weekly aquarium maintenance is necessary. How should we proceed?

II. Prepare for aquarium maintenance

1. Set up a regular maintenance schedule.
It is best to be on the same day every week, not necessarily to be at the same hour. It should become a natural habit of yours. Although we recommended weekly aquarium maintenance, you may do it twice or even three times a week as you wish. While it is not required, at least more frequent partial water change can keep the fish healthier.

2. Get all the necessary equipment and supplies ready for the aquarium maintenance.
Get the following ready: an aquarium vacuum, a few 5-gallon water buckets, and an algae scraper.

3. Prepare new water for fish.
Fish dislike a sudden swing in water temperature. The new water should have a temperature very close to the old water in the tank to avoid shocking the fish. Larger than a 6F difference in water temperatures might result in a shock and even quick deaths of some more sensitive tropical fish species.

That is why we need to prepare one or more buckets of clean water long before we do the water change. Prepare the same amount of water you plan to remove. The new water saved in the buckets need to be treated with your usual aquarium water conditioner to remove chlorine and chloramines. If you have additional aquarium heaters and thermometers, they can be used to heat the clean water in the buckets to make sure the temperature is the same or close to the old water in the fish tank.

Note: For those who use Reverse Osmosis water instead of tap water, you need to add water buffer back into the RO water before letting it sit. Or the PH might crush before you use it.

III. Steps of aquarium maintenance

1. Unplug all the electrical equipment, such as filter, heater.
Better safe than sorry. Fish tank maintenance requires you to put your hands directly into the tank water. Unplug all the electrical equipment first will keep you safe from possible electrical shock in case of a leakage. It will also prevent the filter system from taking up too much debris from the substrate during the maintenance.

2. Partial water change with substrate vacuuming.
By using an aquarium vacuum and a water bucket, you can remove the debris from the substrate and remove the old water from the tank at the same time. You should be gentle while doing this to avoid scaring the fish. Remove only as much water as the available new water you have prepared.

3. Clean the sides of the fish tank.
While some fish hobbyists might prefer to do this step ahead of substrate vacuuming, I do it afterward to avoid creating debris (from the substrate) all over the fish tank during the cleaning. You may use an algae scraper to clean the front and the sides of the fish tank.

For those who have acrylic tanks, we need special algae scraper for acrylic tanks to avoid scratching it. I have also tried it with 100% cotton shirt with excellent results.

4. Refill the aquarium with already prepared clean water
You should carefully do this. Do not dump the water into the fish tank too quickly; it might make a mess of the substrate and scare the fish. Adding new water slowly into the tank can also help fish acclimate to the new change in water perimeter, thus avoiding shock.

5. Clean the aquarium filter
Aquarium filter cleaning is not required every week. You only need to clean it when it is clogged with debris, and you can do it before all the other steps.

To clean the aquarium filter system, you must be extremely careful not to damage the beneficial bacteria in the filter media. You must not wash the filter or the filter media directly under the tap, or in untreated tap water. Chlorine in the tap water can kill the good bacteria and cause your aquarium nitrogen cycle to crash.  You can easily avoid it by using aquarium water conditioner with the tap water in a water bucket. You can also use the old tank water which you have just removed from the aquarium during a water change.

Important Note!
The filter media must not be out of the water for more than a few minutes during the entire cleaning process. The aquarium nitrogen cycle bacteria are aquatic based species, and can’t survive for long in the air.

6. Turn everything back on
Do not forget that you have turned off everything electrical in the fish tank. Now you must turn them back on. You must make sure everything especially the filter and the heater is working properly again. It is necessary to watch the aquarium for at least a few minutes after you have finished everything.  It is to make sure everything is alright.

Additional Tips for partial water change:
For those who have canister filters, things are easier for you. While you still need the aquarium vacuum to clean the substrate for fish waste and other debris, you can remove the tank water from the fish tank, and fill the fish tank again by using the intake and outflow tubes of the filter. This water change method is less stressful for the fish.

For saltwater aquariums, additional work might involve the saltwater mix-up for the new water, as well as clean up the protein skimmer cup during the fish tank maintenance.

Weekly aquarium maintenance does not take more than 15~30 minutes usually.  It is hugely beneficial to help your fish and the whole aquarium system to stay healthy. The little maintenance work can also keep the fish keeper a little more physically active. It is good for you too. Now you can sit back and enjoy the fish after the work is complete.