Stuff Floating in Fish Tank

Many fish growers encounter that mysterious white floating material in their tanks. In some way, this tiny matter’s appearance makes them weary because it has the possibility of ruining fish health. This is why I’ve decided to research more about this mystery.

What is the white stuff floating in my fish tank? Typically, it is composed of protein accumulation, fecal casts, and mulm. It might also be due to an underlying infection such as fungi and worms. Mineral decompositions can also make hard water appear whitish.

Below are a few possible reasons for that floating white material in your fish tank. See if your guess is correct.

Fecal Casts

As mentioned earlier, the white stuff floating in your fish tank might be due to fecal casts. Fish also have cells in the gut that excrete mucus, acting as lubrication, and this helps the contents of their stomach slide through effortlessly.

Some fish growers think that this mucus is a sign of parasitic infestation. However, this is not the case if the white stuff is not moving.


If the white material floating in your fish tank is moving, it is probably worms. Fish tanks are susceptible to attracting planaria and detritus worms that are brought by new plants and fish.

The detritus worms are the ones that look like pointy brownish-white strings. These are not that harmful because they consume plant life and animal waste, not your fish.


In some cases, the white material appearing on the surface of your aquarium is a protein build-up from fish food. The food that your fish doesn’t eat will dissolve and will then release proteins and fats. Clean your fish tank regularly if you don’t want to see this white stuff floating.


Mulm is a term for decomposing organic matter inside a fish tank. It is composed of rotting plants, leftovers, and shed skin. This matter looks like dust and does not float in the water.

So, if the white stuff settles in your filters or on your decorations, plants, and substrate, it’s probably mulm.

Body Oil

Fish growers sometimes place their hands inside the fish tank, which is a possible reason why that white material forms. The body produces a small amount of oil, creating a white film in the water. It is even more possible for fish growers who apply moisturizing hand cream.


Another possible reason for the formation of white stuff in aquariums is mold. When fungi are present in your tank, mold will flourish. The most common areas where you see mold inside the fish tank are your decorations, so make sure to clean them as scheduled.


Cleaning your fish tank regularly might not eliminate the appearance of the white material, and however, it can help you eliminate the possibility of pest infestation of your fish. Also, check out other ways to keep the fish tank clean and safe against infestations to keep this white stuff at bay.