Why Is My Aquarium Water Foamy? (And What To Do About It)

why is my aquarium water foamy? That is a question quickly asked as soon as this phenomenon occurs in someone’s aquarium. Imagine you have an aquarium with fantastic fish and incredibly beautiful live plants. You put a lot of energy and time into it, but you discover that you are suffering from water that is soggy. 

There are many reasons why this can happen and that is exactly why I am writing this article. When this happened to me the first time, I did not know what to do and spent hours looking for an answer online. This blog is for anyone who suffers from an aquarium with foamy water. 

Here are the reasons why your aquarium water is foamy and what you can do about it!

why is my aquarium water foamy?

Firstly, it’s good to know that foam can have many different causes. Some, but not all, of these are bad for your fish. Below are the different reasons why foam appears in your aquarium.


Agitation is the first thing to take into account. Shake a liquid hard enough and it will form foam. Even if you shake the water hard enough, this will happen. If you are changing your water and you refill your aquarium (and you do this hard enough) you can cause the foam to form. In itself, nothing to worry about, and this is in principle somewhat normal. Do you want it to stop? Then make sure you calmly pour the water into your aquarium. 

What works even better is to use a plate. Hold the plate at an angle to the aquarium and pour the water into the aquarium via the plate. This way, you can be sure that the water will flow gently into the aquarium.

Spray bar or powerheads

This may not be a secret to you, but spray bars and powerheads can also cause agitation in the water and ultimately create foam. It is important to know that this type of foam is not at all harmful to your fish. It will not kill your fish! You will usually see that these bubbles disappear again fairly quickly.

Protein accumulation

Well, this might be less obvious. Protein accumulation can cause foam in your aquarium. This is a protein-based waste. How does this work exactly? Protein buildup can cause debris to remain and this debris can form a coating around tiny air bubbles. Normally, these air bubbles would quickly disappear, but the coating causes them to stick together, resulting in a layer of foam that stinks. Now, this happens more often in saltwater aquariums, but it is good to know that this can also happen in freshwater aquariums. 

So how do you solve foam caused by protein buildup?

The solution is actually quite simple. If your foam is caused by protein buildup, it’s time to give your aquarium a good clean! That way you can at least make sure that all impurities are removed from your aquarium. It is also a good idea to install a protein skimmer. These work hard to get rid of the excess protein. 

Another thing you can/should keep an eye on is the fact that protein build-up can also be caused by a fish dying (without you noticing it). When a fish is in the water for a long time it will disintegrate and this can also be a source of protein. This can also be the case with dying plants. This is why it is useful to visit your aquarium every day and check that everything is healthy and alive!

Soap creates foam

This one almost speaks for itself, but soap residues are also a source of foam in your aquarium. If you have cleaned your aquarium and filled it up with water again, you may find that this was not done properly and that soap residue has remained. In order to avoid this, you should always ensure that the tools you use to clean your aquarium are not used for other cleaning tasks (e.g. scrubbing pads, and water buckets).

Should this be the case for you, there is really only one thing you can do about it. Empty your aquarium, clean it and fill it again with clean, dechlorinated water. Also check your filter and filter pads, as these may also have soap residue. Of course, you don’t want to have to empty your tank again to clean it and refill it!

bubble nest foam in an aquarium

Another thing that can create foam in your aquarium is a bubble nest. Some male fish create a sticky, frothy bubble nest and do this to attract females to mate. 

If this happens, you can be sure of the following: Your male fish are giving an indication that they are healthy and happy with the conditions. Otherwise, this will not happen. So, creating a bubble nest is part of the mating process and they hope that a female will swim through the frothy bubble nest and start the mating process. 

The best thing you can do when you see a bubble nest is to leave it alone. If you don’t, you will find that your male fish become stressed. 

The dechlor you are using

If you find that you get foamy water that surfaces from the filter, it can be caused by the dechlor that you are using. Sometimes when you use dechlor that contains aloe or “slime coat protector”, you might find that it causes your foamy bubbles. This is fairly easy to solve by increasing the surface agitation (a point I spoke earlier in this article about) by lowering the water level so there is more splashing involved. 

If you have a canister, you can try and aim it to the spray bar (so that it would spray across the surface of the tank).

How to get rid of foam bubbles in your fish tank?

Now that you’ve read this far, you might find that you don’t need more tips or a summary of what we discussed, but to be thorough, here are the things you can do to get rid of the foamy bubbles in your tank.

1 – When you’ve established that protein foam is the case, you should give your aquarium a good cleaning. Clean (or replace) the filter and remove any dead plants and fish. It is also wise to clean the tank of other debris.

2 – As we’ve discussed earlier… Leave the bubble nest in touch because you do not want to stress out your fish.

3 – When the bubbles are caused by oxygen-rich water, you can let it go. It normally should go away within a matter of days. If not, simply wipe them away.

4 – When the bubbles are there when you do a water change, it might be smart to do the water change at a slower tempo. Don’t rush and let the water go slowly in the tank. You can also make use of a plate. Let the water roll down slowly over the plate so that you can fill your tank slow and without bubbles.

5 – It can be that the foam bubbles you see are there because of soap residue. Let the water run out of the tank and clean all the materials, tools, and the tank thoroughly. After that add fresh water to it and everything should be fine.

Final thoughts

As you’ve seen, there are a lot of possible reasons why you have bubbles in your aquarium. Not all of them are bad for your fish, but some are. Therefore you should take proper action once you’ve identified what is causing the foam bubbles. Most of the time it is easy to solve!