7 Reasons That Causes Air Bubbles or Foam in Your Fish Tank

Have you ever seen bubbles or foam in your aquarium water surface and wondered to yourself, is that normal? is it dangerous? Keep reading as I share seven reasons why you may be seeing bubbles popping up in your fish tank.

I think the first time I saw weird bubbles was in my quarantine tank. There was a sponge filter in there, but for some reason, the bubbles weren’t popping, and I was like, that’s kind of strange.

Air stone, a sponge filter or a bubbler

So out of the seven reasons why you might see bubbles in your aquarium, I’m going to quickly go through number one, which is the obvious one. If you have an air stone, a sponge filter, a bubbler, or any kind of air-driven device where you’re using an air pump to deliberately pump air into your aquarium, obviously you’re going to see bubbles.

Now, those bubbles should be clear. They should not have any kind of color or tint to them, and they should pop immediately when they get to the surface.

Bubbles after a water change

Reason number two is pretty common as well, and that’s bubbles after a water change. But do you ever wonder yourself, why are there sometimes bubbles after a water change? And sometimes there are.

Well it has to do with the temperature. So if it is cold outside, it’s in the winter, the water coming from the ground is very cold. It suddenly gets warmed up and then put in your warm tropical aquarium.

Now cold water can hold more oxygen than hot water, so the oxygen filled cold water comes here and all of a sudden in the warm temperature it has to get released. And therefore, you’ll see little bubbles all over the decorations and plants in your aquarium.

Now, nothing to worry about, just wait a few hours, those little bubbles should pop. But if you see a ton of micro bubbles all on the aquarium walls, usually that means not only was there a large temperature difference, but maybe a large water change was also done as well. So in that case, go ahead and keep a closer eye on your aquarium just for the next few hours or days, because large water changes sometimes means hugely swinging water parameters, which may affect your fish’s health.

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Number three is medications. So certain medications like Praziquantel, Pimafix, Melafix have been known to foam up, because what they’re doing is changing the viscosity or thickness of the water.

So if you have an air stone or a sponge filter in your aquarium, normally those bubbles would pop right away. But because now the water is thicker, the bubbles take a lot longer to pop. And you’ll notice a similar theme with some of the other items on this list.

Now, from what I’ve seen, the medication foam tends to produce clearish, transparent bubbles, at least from the ones I’ve used. So if you see bubbles that have like a oily, rainbow, iridescent kind of sheen to it, it could be from soap or cleaning products, which is an absolute no-no.

So public service announcement, if you need to clean something in your aquarium, don’t use normal soap or those kind of cleaning products. You want to use hot water and something like chlorine or bleach to sanitize and disinfect your equipment and decor.

Biofilm on the surface water

Speaking of oily bubbles, number four is if you have an oil slick or some kind of thick, translucent biofilm on the surface of the water, that can often trap any bubbles that would float up normally and pop at the surface.

So what that’s caused by is if you’re feeding certain oily fish foods, it may come off the oil from your hands if they’re unwashed when they go in the tank. And any sort of organic oils and proteins that have floated up to the top.

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And a lot of people recommend getting rid of it by using a paper towel to soak up some of those oils. But to me, that’s a very short term option, and it’s actually more indicative of another problem.

A lack of surface agitation. Surface agitation is what causes gas exchange to happen in your aquarium, and therefore carbon dioxide can leave the tank and more oxygen can enter it for your fish.

So to get more surface agitation and oxygen for your fish, you want to use something like a sponge filter where the bubbles rise up. They’re going to pop at the surface and cause the water to move and it’ll break up that oil slick. Or if you have a different kind of filter, you can aim the output at the surface so that again, it breaks up the surface, allowing that oil to dissipate and then the oxygen to get back into the water.

Excess ammonia

Number five is excess ammonia. Now you’re only going to see this if you have a air stone or sponge filter causing bubbles. But this is very similar to outside. If you see, like near a cattle farm, there’s a lot of run off going into a nearby waterway, and then there’s foaming in the water.

So, that’s the same thing going on with the excess ammonia. And a lot of times you may see this in any of your aquariums that are heavily stocked, high bioload, that kind of thing. Or maybe outside in an outdoor mini pond where there’s lots of leaves and debris falling into the water and causing that nutrient spike. So just something to be aware of, again. If you see bubbles, maybe get that test kit.

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Bubble nests created by your fish

Number six is a good one. It’s bubble nests created by your gourami, betta fish, or another bubble nester.

Where, basically the male will use his saliva to create tiny little bubbles into this big foamy nest, typically in a corner of the aquarium where there’s not a lot of surface agitation, or maybe between a lot of floating plants.

And in the wild at least, or if you choose to breed your fish, they will create that bubble nest. They will court a female and mate with her, and then gather up all the eggs using his mouth and spit them in the bubble nest. There, he will guard them until they hatch a few days later.

Pearling coming from plants

Reason number seven is my favorite. Pearling coming from plants. So part of photosynthesis, during the daytime the plants will consume carbon dioxide and they will release oxygen. And if your aquarium water already has so much oxygen that it can’t take it anymore, you’ll see little bubbles form, like on the leaves of this Java Fern over here.

Or right now, this crypt is actively causing a stream of bubbles float to the surface. Very cool. Unfortunately, you might also see it with any algae that is in your aquarium. Like on my heater over there, there’s a bunch of bubbles. That is definitely caused by the algae also photosynthesizing. Not very pretty, but it is healthy for the ecosystem of your aquarium.

bubbles can be a sign of either something dangerous or something healthy going on your aquarium, just something to keep your eye on.