Noticing that a white foam has been created across your tank water can sometimes trigger various concerns. Indeed, it is often a sign that something is not really right, and that you may need to intervene in order to allow your tank water to return to normal values.

However, this can sometimes also indicate a purely natural situation during which your water parameters remain intact and there is nothing needed to worry about.

Therefore, knowing the main causes and the appropriately possible solutions for white foam in aquariums is really important. To ease that on you, we are sharing our guide below.

Foam on Aquarium Water Surface

So, here are the main causes of white foam on the water surface in fish tanks:

– Dirty Water

Quite often, noticing foam on the surface of your tank water is actually a clear sign indicating that all that needs to be done is a good cleaning. Indeed, dirty water becomes foamy eventually.

Overstocked aquariums, not enough cleaning activities, inappropriate filtration systems or any excessive debris can lead to dirty water conditions. Therefore, a good cleaning action is all you need.

While doing so, remember to perform a partial water change but also to rinse the filter as well as to vacuum the gravel. If you are not sure whether you have done a thorough job, you can double-check the state of your water by simply using a testing kit.

If ammonia or nitrites are above zero, you should probably take some additional measures.

– Water Aeration

As with any other liquid matter, small bubbles will eventually be formed if you agitate it long enough. Water aeration only means that the tank liquid has been unrested, either due to a partial water change that just happened or because of the way your bubble stone works.

In any way, this a completely normal cause of white foam across an aquarium and there is absolutely nothing to worry about here.

If you would like to reduce the water aeration during partial water changes, you can help yourself with a simple plate.

Instead of pouring the fresh water into the tank directly from the bucket, try pouring it on a plate first and then into the aquarium. This should reduce the bubbles by much.

– Biofilm and Protein Buildup

Here is another perfectly valid reason which can force you to clean your tank immediately. Fish waste, their meaty food residues, small dead fish which go unnoticed or any other decomposing matter containing proteins can eventually link itself to the air bubbles and coat them with a smelly surface.

This will gather the bubbles around one area of the tank, and you should be able to smell it when nearby.

When this happens, please ensure that such tank gets thoroughly cleaned, as well as the water inside it. Vacuum your tank substrate and clean it out from any potential debris present, but also ensure to rinse the filter into tank water.

Next, performing partial water changes is crucially important and it is the only certain way of allowing the water parameters staying stable and your tank clean. Therefore, never disregard its vital importance.

If you have such aquarium which allows for food leftovers and fish waste to be scooped immediately after being released to the tank bottom, do not hesitate to clean those materials out.

The same goes for live plants across the tank. If you notice some leaves which do not seem healthy anymore, remove them.

– Bubble Nest

Finally, one cause of water foam which is perfectly safe and actually fun to observe- bubble nests! The most famous designers of such are definitely male betta fish, but there are several other fish species which use to do them.

Bubble nests consist of simple air bubbles which are later coated in the saliva of the fish which create it. That way, they stick together at the top of the tank and form a somehow of a safe place for fish fry.

Such bubble nests can vary both in shape and size depending on the fish species which constructs them, but also on the individual size of the specimen.

Being mainly produced by males, noticing a bubble nest does not always have to be an indication that you will soon be facing baby fish across your tank. In fact, some individuals decide to construct them non-dependent on babies arriving soon.

Destroying the bubble nest will certainly not hurt the feelings of your pets, but you can also decide to leave them, as they do not influence the quality of the water.

– Fish Medication

If you are using medication to treat your ill fish, there may be some white foam emerging to the tank top. Or, more precisely, water bubbles.

This usually happens because medication slightly alters the water hardness, making it thicker. Consequentially, air bubbles that are coated in medication will not pop up immediately when reaching the surface, but they will rather be more resistant and require a bit more time to dissolve.  

It is fine not to mess with fish medication bubbles, as such products are completely safe for your pets. However, what you can do is to isolate your sick fish inside a temporary tank while treating them with medication.

Wrapping Up

White foam across an aquarium can sometimes be a deadly sign indicating that something is seriously wrong with the water quality, but it can also be a perfectly normal occurrence that does not require any intervention from your side. Therefore, knowing what usually causes such bubbles being visible is crucial.  

As a general rule, bubbles which are pristine clear and pop up as soon as they reach the water surface should be safe. Except for bubble nests, which tend to endure longer thanks to the saliva they are coated in.

On the contrary, the dirty foam which sticks to the top and is visibly yellowish or features any oily coating is often a sign showcasing that your tank needs a good cleaning.

And finally, if you are not sure of the reasons causing your water to foam up, testing your water parameters should let you know if everything is all right or not.

Written by Fabian

Hey, I'm Fabian, chief editor at Aquarium Nexus. I really enjoy the aquarium hobby and love sharing my experience with others. If you have any questions feel free to contact me or leave a comment below.

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