How Often Should I Clean My Fish Tank?

How often should I clean my fish tank? Aquariums are a worthwhile investment that can liven up any room. While it’s necessary to clean your aquarium, how often you do it depends on several factors:

  • The type of fish that live in it.
  • The quality of your water.
  • The size of your tank.

Ideally, it would be best if you clean your aquarium weekly while monitoring it every day. Doing these may sound like a chore, but it prevents you from a major overhaul that could potentially kill your fish. Slow changes in the water chemistry could cause tragic long-term effects in the aquarium, so it’s essential to keep a close eye on it daily.

Clearing debris, fish waste, and excess food can be done without changing the water, as the tank’s water filter removes these. An aquarium of any size should have 10% to 15% of its water changed every week, and you should replace filter cartridges every month.


Why do I need to test my aquarium water?

Fish waste secretes ammonia that harms your fish if left to stagnate. Over time, the tank itself will smell bad and become more acidic – which is why regular water changes are necessary for small increments. The goal is to keep pH levels balanced since ammonia and nitrate are the compounds that could make or break your aquarium’s ecosystem.

Regular water testing comes hand in hand with monitoring. By keeping tabs on any irregular spikes in ammonia, nitrate, and phosphate, you spare your fish from stress and untimely death. These chemicals don’t easily get filtered out and need to be extracted manually. It’s a grueling but necessary task – but remember that prevention is better than a cure.

old tank


Why is it important to clean my fish tank? 

Over time, the aquarium will collect all the extra food, fish waste, and minerals that have been pumped into it. Some of these things get filtered, but most of it stays in the tank unless manually removed.

One harmful substance that could slowly kill off your fish is ammonia – which is produced naturally as a waste product. Ammonia doesn’t instantly kill your fish, but its gradual accumulation will make your fish look groggy and sickly. If neglected for an extended period, the tank will end up smelling utterly foul.

Besides the foul smell, ammonia increases the acidity of the water. This gradually poisons all the life in the tank – which is risky because it goes unnoticed at first. If you’ve left your aquarium untouched for months because you see that the fish are still alive, chances are they’re already sick.


Can I save sick fish by replacing all the water in the tank? 

Unfortunately, suddenly changing the water in an ammonia-filled tank will be devastating to your fish. It’s likely to cause new tank syndrome – which kills off your fish because they’re not used to clean water chemistry.


Essential bacteria take about two months to develop in an aquarium. The sudden removal of that will mess up with the equilibrium of your fish – leading up to their death. 

Similarly, this is also referred to as old tank syndrome – which is when an aquarium’s water quality degrades, and the fish adapt to the toxicity. Upon suddenly changing this nasty water into clean water, the fish die because they’re not used to the lack of chemicals.


What is old tank syndrome? 

When an aquarium has been left at the mercy of time and neglect, it will eventually turn into a living nightmare. Old tank syndrome is the slow degradation of tank water that gradually affects your tank filters, fish, and eventually you – the owner.

There’s more to old tank syndrome than just dirty water and algae overgrowth. The killer is unseen and lurking in your fish. Harmful bacteria and chemicals are now heavily incorporated in their bodies – so much so that they look totally fine on the outside. 

Smaller fish die out while the larger ones carry on swimming about. Usually, aquarium owners react to the sudden dying out of fish by merely adding new fish – blissfully unaware that the new fish can’t handle the toxicity of the old tank water. Unchanged tank water has too acidic pH levels that are harmful to new fish, bad for your older fish, and dangerous.

Old tank syndrome occurs when an aquarium is neglected, and therefore can be avoided entirely. As a responsible fish tank owner, it’s vital that you closely monitor your fish and perform the needed water changes to maintain a happy, healthy, thriving aquarium.


Why do I need to keep track of my fish? 

Daily monitoring of your water should be paired with counting your fish. Seasoned aquarium enthusiasts encourage using logbooks, especially for medium and large tanks that can house up to sixty gallons. 

If your aquarium houses various fish, the first ones to be affected by an uncleaned tank are the smaller fish. Besides monitoring the water, it’s crucial you also keep a tally of your fish. Some fish die out without you noticing because they sink to the bottom of the tank. If you notice a diminishing number of fish, it should alert you to take the necessary steps of cleaning the tank.

Even when you can’t test the water, you can keep track of your fish. This is as simple as checking the bottom to see if any dead fish may have sunk. A varied collection of fish may be easier to monitor – but watch out if any of the larger ones eat the smaller ones.


How do I change the water in my fish tank? 

As mentioned, careful and gradual water changes are best for aquarium maintenance. Regardless of tank size, a 15% – 20% water change should be performed weekly. This could vary when considering the number of fish in the tank and the size of these fish.

A siphon tube is used– and this usually comes with a gravel vacuum that removes algae and debris. As you remove water from the tank, do so gradually to not stress out your fish. Submerge the hose in the tank, and once full, block out the open end with your thumb and spill out the collected water into a pail.


You must keep this old water, as you can use it to clean your filters. This old water contains essential bacteria accumulated over the past few months and help maintain the ecosystem that your tank has established. Never use new tap water to rinse filters because this will eliminate all the good bacteria.

Keep in mind that chlorinated tap water should be dechlorinated or left to sit overnight in a bucket before incorporating it into the aquarium. Also, never clean any of these materials with soap, as it could also kill the essential bacteria. The rule of thumb here is to keep, use, and incorporate as much of the old tank water as possible.


What type of water filters can I use for my fish tank? 

Filters are available in mechanical, chemical, and biological forms. Each of these does about the same thing but vary in performance and effect. You should get familiar with them and figure out which best suits your fish tank.

Biological filters are the easiest to maintain, as they are natural and don’t need to be cleaned often. They usually come in the form of moss balls. If the need arises for them to be cleaned, especially during the water change, you must use the old tank water to rinse them.

Meanwhile, mechanical filters have foams that need cleaning once a month. These should not be cleaned at the same time during water changes – as doing so might affect your fish. Ideally, cleaning the filter of your mechanical filter should be done a week after – only by rinsing it in old tank water, removing the scum with your hands, and replacing the sponge with a new one.

Lastly, if your tank has chemical filters, be sure to have these changed every three to four weeks – preferably changing them as you’re changing the water as well. Chemical filters are carbon filters that help regulate the chlorine, ammonia, and texture of the water. So, if you notice your water getting cloudy often, take this as a sign to change the filters as soon as possible. 

Thanks to your fish tank

The care and maintenance you put into your fish tank is time well spent. Nothing beats caring for a little ecosystem that you can observe and appreciate. While also educational, it also provides a stress reliever and even encourages introspection and meditation.

It’s not a simple task to keep a bunch of little critters alive, but there is something quite fascinating about caring for them. Over time, you won’t even need to think about maintenance – as it may come as a reflex to look after your precious fish. As long as you have the heart for it, your aquarium will liven up your home for the years to come.




Rita Wagener
Rita is a resident paw expert at Pet Keepers. A registered & licensed dog trainer, she also has a degree in animal nutrition, and runs her own dog training course.

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