How To Keep Fish Tank Clean From Algae and Dirt

There are cases where you see a nice but dirty fish tank. It destroys the look and it needs to be clean immediately! Algae and dirt are really destroying the look of the tank! That made me wonder:

How to keep a fish tank clean from algae and dirt? The best way to keep a fish tank clean is to do regular water changes and scrape the algae off. Be sure the filter is changed regularly.

By keeping the fish tank clean you will have clear water and the fish tank will generally look nice. Here I will go through every step of keeping a fish tank crystal clear and free of algae and dirt.

The filter

Most of the work of removing dirt is actually not coming from you doing anything.

It’s coming from the small creatures living inside your filter and everywhere in the fish tank. It’s the bacteria breaking down organic material that is doing most of the cleaning in the fish tank.

The bacteria are living on everything, in the substrate, on the rocks, or the wood in the fish tank. But they are mainly living inside the filter in the filter media.

The filter is inside a pump. How the filter looks is different but the most common one is a filter that you put inside the fish tank.

When water gets sucked up by the pump. Then the water goes through the filter where a lot of debris gets stuck and then the water continues out, back into the fish tank again through the nozzle you have at your pump.

The debris getting stuck in the filter will decompose by the bacteria. The matter getting stuck is feces from fish, dead leaves, and rests of food mainly.

All this debris will sink to the bottom and collect during the years of the fish tank being used. This could be a cause of algae growing since there are a lot of nutritions in this dirt.

By increasing the pumping power the pump will take water, and with it debris, all the way from the bottom. This will bring all this dirt into the filter and let the bacteria work on it.

It’s a higher concentration of bacteria in the filter than what it is outside in the fish tank. Therefore the bacteria will work better inside a filter than what they do at the bottom of the tank.

Slow workers

The bacteria are not very fast workers though.

If too much debris is collecting inside the filter due to too much fish or that you have a too effective pump it builds up and will not be decomposed properly. This will send out particles of the debris, out into the fish tank again. Making it dirty again.

The most common type of filter media is the sponge filter. It’s a sponge that collects the debris and lets the bacteria get to it. The sponge filter will clog quite quickly and be less effective so you have to change it at least every month.

By doing so the filter will be clean and will pick up the debris more effectively.

You could also “clean” the sponge when doing water changes. I say it in quotations because you don’t really want to clean the filter. Bacteria are living there and you don’t want to kill them. All you want to do is to remove the debris, making the pump more effective and also making the breakdown of organic material more effective.

To “clean” the sponge you just dip it in the fish tank water you have siphoned out during a water change. There are bacteria in that water which makes it a great option for removing debris without killing the bacteria.

If you clean it in your sink, the bacteria will die due to the chlorine that is in the tap water.

When you have “cleaned” the filter or if changing the sponge, you should always add starting bacteria helping the bacteria out to re-colonize the filter again.

The starting bacteria is brand new bacteria and includes “food” for the bacteria to help them grow. Bacteria are your best friends! On my recommended necessities page you will find which starting bacteria I use and recommend.

Scrape algae off

Algae will make the fish tank look dirty.

There are a lot of different types of algae. The most common, and the one a lot of people think of when thinking of algae and a dirty fish tank is the green spot algae.

Green spot algae are the green spots accumulating at the glass of the fish tank. These are usually pretty hard anchored towards the glass so they need a bit of force to be removed.

One way is to scrape them with a magnetic algae scraper. It’s those types of scrapers where you have one part inside the fish tank and the other outside. They get stuck against each other on either side by magnets, which could be quite strong.

This kind of scraper could do the job but most often than not they are just doing a so-so job by scraping the algae off. Also if you drop the part inside the fish tank, there is a risk of it has a small stone stuck and that will scratch your fish tank window.

An alternative to the scraper is to use a credit card or a membership card that you don’t use anymore to scrape the window with.

This also requires some force to be able to scrape the green spot algae off. with this method, you don’t run the risk of dropping it and get stones inside scratching the window.

There are also tools to scrape the algae off with a razor blade attached. It’s similar to the credit card method but with a sharper edge, which makes you use less force to remove the algae.

If you have other types of algae you should take care of them. Depending on the type of algae there are different methods of removing the algae. I have an article going through exactly how to remove algae if you have an algae problem.

Water change

It’s one thing to clean an already dirty tank but it’s better to prevent the fish tank from getting dirty in the first place.

The best weapon you have in your arsenal is to do regular water changes. It’s very important to make this a habit when keeping fish.

If you have a smaller fish tank, you have to do water changes more regularly because the dirt will build up quicker than it will in a large fish tank.

Therefore it’s recommended to have a large fish tank, especially for beginners. The maintenance will be less of a hassle when having a larger fish tank.

The fish that you have in your fish tank is doing everything in their living environment, the water. They eat, swim, and they do their need there. A fish tank is an enclosed environment and everything builds up during the time.

First of all, you have to feed your fish. This is a cause of giving nutrients to the water and then give fuel for algae to grow.

Secondly, your fish are releasing stuff into their water too. It will also give nutrients dissolved into the water and that will add to the fuel of algae growth.

When doing a water change you remove some of the water in the fish tank and replace it with new water. The new water you replace it with comes from the tap and are not including the nutrients.

When replacing the water you dilute the nutrients in the fish tank by making the nutrients less when you remove the water.

By doing this regularly you will keep the unnecessary nutrients at bay and it will not fuel the algae growth.

When doing a water change, you not only can change the water. You will also remove dead leaves and other visible matter at the bottom. This will break down into dirt by the bacteria, so pick it up and throw it away and let it be dirt anywhere else than inside your fish tank.

Siphon the bottom?

Food and excrements are collecting at the bottom of the fish tank. When siphoning out the water, should you siphon the dirt off from the bottom?

Sometimes you could remove excess dirt accumulating. But don’t do it regularly! You will remove good bacteria living in the substrate risking a problem with the balance of the water.

A tip is to scrub your rocks and stones with a sponge (that you only use for the fish tank) lightly to remove dirt and algae growing there. Do it before you change the water so you can suck up any particles floating in the water.

This will make the tank look cleaner. But if you are going for an “older” look, the small algae that will grow on the rocks might be a look you want.


The amount and type of is you are putting in your fish tank are also making an impact on how dirty your fish tank will be and how often you have to do something to keep it clean.

If you put too much fish in the fish tank it could cause a problem. All these fish are pooping in the water and giving it the nutrients into the water as I described above.

More fish equals more poop and more poop equals more nutrients and more nutrients equal more dirt and algae accumulating.

The recommended amount of fish to put in a fish tank is one inch (3 cm) per gallon (4 liters) of water.

By following this rule you will have a good amount of fish doing their number two while the filter can help with the cleaning. Also, the water amount will be sufficient enough to dilute the nutrients.

Dirty fish

Some fish are dirtier than others. A very common and very dirty fish is the goldfish.

The goldfish are more common in ponds though because they could get very big. Also because they give off a lot of poop, it’s better to have them in a pond rather than a fish tank.

A better alternative is the Veiltail fish. It’s more suitable in a fish tank and is a type of goldfish. They still need a larger fish tank though since they still are a very “dirty” fish.

So if you want a clean fish tank with less maintenance, you should not go with these fish.

Clean fish

Some fish are “cleaner” than others too. These fishes poop too tough so the nutrients from their poop are still getting into the water.

What makes these fishes considered cleaner is that they will eat algae, cleaning your fish tank from letting algae grow.

One fish is the Otocinclus catfish which is a quite small fish and not very visible in the fish tank. That’sbecause they are everywhere and are of dark color. They are very well camouflaged in a fish tank with dark substrate.

These are constantly swimming around and eat algae. You should have a school of these fishes and that makes them very effective cleaning the fish tank.

Also, a fish called Siamese algae eaters are a good addition to keep the algae at bay.

The Ancistrus are generally sold as a cleaner but that’s generally true in their early life. Later on, when they grow, they will get lazy and will not eat algae at all.

When they are large they produce more waste than what they remove so an Ancistrus is nothing I would recommend when going for a “cleaning fish”.

Note that by putting in “cleaning fish” you will not get rid of any problems with a dirty tank. The fish is only eating algae but are producing waste too and to not get a problem with too much waste you should still make regular water changes and keep the cleaning routine.

If you have an algae problem, don’t buy “cleaner fish”. Instead, get rid of the problem causing the algae to bloom. That way you will have a cleaner, more nice-looking fish tank in the long run.

Less feeding

You have to give your fish food. Food contains nutrients for your fish that they need. It will also release the nutrients into the water and could give you an algae problem.

If you feed too much the food will accumulate at the bottom of the tank and it will be getting composed by the bacteria and leaving a “dirty” mass at the bottom.

The optimal amount of food to give your fish is enough for them to eat within 2 minutes. How much that is is depending on how many fish you have.

In the beginning, it’s better to feed a little less to be sure you are not overfeeding them. It’s very common to think that the fish is getting too little food.

But in reality, it’s the opposite. Usually, you give too much food and that’s dangerous for the water quality in the tank. The fish will survive a long time without food, so it’s better to feed them too little than too much.

After a while, you will get a feeling of how much to feed the fish for them to eat it all up within 2 minutes.

It’s important to give the fish good quality food too. Good quality food should contain ingredients that give your fish the right nutrients. Also, the right type of food should not release particles into the water when you feed your fish.

These particles will fall to the bottom and build up grime in your fish tank and potentially destroy the water balance.

To be sure you choose the right type of food for your fish I have written this article where you will be taught everything about the food you give your fish.

If you feed your fish food that will accumulate at the bottom, you could have bottom feeders that will eat the food at the bottom.

These types of fish should not be fed solely on leftovers from the other fish, they need other food too.

Their main meal should be specific wafers that will sink to the bottom for them to feed on.

Getting these types of fish are not a reliable way to get rid of the accumulation of fish food in the substrate. Instead, you should feed your fish less to get rid of this cause of a dirty fish tank.

Shrimps and Snails

You could put inhabitants into your fish tank that will clean it from algae and leftovers that are not fish.

Those inhabitants are shrimps and snails. These creatures are eating algae and leftover food and are quite happy with it.

Also, they are not producing a lot of waste products as fish do.

Every fish tank will benefit from having shrimps and snails due to their capabilities to clean. Now, shrimps are not as good of a cleaner as snails are but they are generally considered nicer to look at than snails.

The Amano shrimp is the best cleaner of shrimps. It cleans algae and is very good to get to the algae where other inhabitants might have a harder time reaching.

The smallest crack in a rock is possible for the Amano to clean.

The Amano shrimp are almost invisible which makes it hard to find and look at. It’s just there somewhere doing its work.

What’s not as invisible as the Amano shrimp is the snails you can (and should) put into your fish tank. The snails are a very good cleaner, eating everything from algae to leftover food that has accumulated at the bottom.

The snails are not that invisible because they tend to reproduce a lot. The dirtier the fish tank (which equals more food) the more snails you will have.

It’s easy for them to get out of control if the fish tank is dirty because there is a buffet of food for them which makes them reproduce a lot. If you get control of the environment the snails will be kept at a manageable level, making the snails not be as noticeable in the tank.

There are a lot of different snails that you can put inside a fish tank. Almost all of them are good cleaners.

The ramshorn snail is one of the best algae eaters there is and is a very common snail to have. It’s available in a lot of different colors.

The nerite snail is also a very common type of snail. It’s a quite dark snail and is not as noticeable in the fish tank as other types of snails might be. The nerite snail is still a good cleaner in the tank.

The snails have the same upside as the shrimps have. They can get everywhere to clean! No matter how small the crack is, the snail and the shrimp will be able to get in there and clean.

You should not let your shrimps and snails only rely on leftovers. You should feed them other food too.

This makes it that you still need to have control over the water and feeding of your fish to be able to have a clean tank. You should not count solely on snails and shrimps to clean the fish tank.

You will get an infestation of snails if you rely on them cleaning the tank and, generally, that’s unwanted.

Cleaning fish tank before starting it

When buying a new or used fish tank you should clean it before putting water into it and start to cycle the tank.

That is to remove any chemicals that might be present inside the fish tank and also, if it’s a used tank, remove any algae, dirt, or minerals that are stuck on the glass.

If you fill up an uncleaned fish tank with water, the dirt and algae will get introduced into the water and giving it a chance of “infecting” the water straight away, before even putting in any fish.

If the tank is containing any chemicals, you might have a harder time cycling the tank to build up bacteria in the water, thus making you have a fish tank that’s never getting the right water balance.

Without the right water balance, you will have a problem with algae growing and dirt accumulating.

If you buy a brand new tank from a pet store, there are generally not any problems with algae or dirt being in the fish tank. There should be no chemicals inside the fish tank either but to be sure it’s best to clean it.

If the fish tank is used, you should be sure what has been inside it. If it’s cleaned with chemicals it’s best to pass on the tank from the beginning since it could damage your inhabitants, no matter how good you clean the tank.

How to clean a fish tank before starting it

In the beginning, you should have a spray bottle with water and vinegar.

Spray the inside of the tank with the vinegar solution and clean the inside with a sponge. You should be able to scrape a lot of dirt and algae off the glass.

Not all dirt and algae will be removed from the inside. To remove the rest, you should get an algae scraper and scrape the rest off.

When you have gone through every side and corner of the fish tank, remove the last bit by spraying some of the vinegar solution and clean it off with the sponge once again.

Lastly, before putting water in the fish tank. Spray the inside with water and remove it with a clean rag. That way you will remove any vinegar solution that might be left inside.


Keep your fish tank clean from dirt and algae should not be a hard task if you maintain your fish tank the right way.

By doing regular water changes and don’t feed your fish too much, you should be able to keep a good balance in the water and by doing so, you should have a clean, clear, and nice-looking fish tank to enjoy.

The measures you should do by keeping the fish tank clean are not taking a lot of time. It will be a maximum of an hour per week to maintain the fish tank.

If you consider how many hours you will enjoy your fish tank after that, it’s not a lot of time to claim for the maintenance.

Also, consider putting some cleaners into your fish tank to help keep the balance right. The best cleaners are snails since they don’t produce too much waste and eat what is the main problem with a dirty tank, algae, and leftover food.

The snails are also self-regulating the amounts depending on how much food they have available. That will give you an indication of if you might have a problem with a dirty tank or not.


I have been a fish keeper a big part of my life. During the years I have gathered and searched a lot of information about fish keeping and here, on the website, is where I share that information to help you with your fish keeping. I want to provide the information that I didn't get when I had a question about my fish tank.

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