Got another question for you all today...

I used to notice this white fuzzy stuff on the black sponge biological filters in my Whisper 60. It appears on the exposed portion above the water, and sometimes also on other parts of the unit. I trimmed off the portion of the sponges that were above water, and have had no more fuzz on them.

Tonight I took the cover off my whisper 40 on my QT tank, and noticed the same icky white fuzz on the filter cartridge.



Is it mold? Some kind of bizarre algae? The fuzziness of it makes me think it's not some sort of hard water deposit or similar buildup. I can't help wondering if it could have something to do with my fishes' health issues.

Anyone else see this stuff before?

Ew, looks like mold. I've never had it grow on any of my filters, so I think it might be a good idea to change out that media. Do you have extra media that could support your aquarium?

This was actually the cheaper Top Fin brand filter, which did not come with biological filter media (the black sponge), I have not seen these sold separately in stores, and I haven't gotten around to buying one online 'cause the quarantine tank was only meant to be a temporary situation..

Anyway, this one Biobag cartridge is the only filter media in the aquarium. I'm afraid that if I change the bag, I will lose the bacteria. Of course, dealing with that is a better option than letting the mold continue to grow.

Do you have high nitrites/nitrates? How's the ammonia level? The fuzz looks like what shows up before mushrooms start growing.

That looks like the mold you sometimes get on really rotten fruit.
It can't be algae... and as far as I can tell that's some kind of mold.

Even with the 'infected' part removed you need to be really careful because mold can be tricky to get rid of. Just keep checking the filters and your entire tank in general at least once a week and if the mold returns, remove whatever it's on, toss it, clean the water/tank as you see fit, and continue to watch closely.

Mold can be extremely harmful to well, any life... because mold is so genetically diverse, it's nearly impossible to tell with any certainty if the mold you have is releasing deadly chemicals or not.


I may not be a goldfish expert, but I know a lot about simple organisms (environmental science and AP Biology... you sort of have to force all this stuff into your brain.)

MUSHROOMS?! Seriously? Ack!

I change at least 1/3 of the water every other day so I haven't tested the water recently, but with the green cloudy water I've got at the moment, I'm guessing there's a bit of nitrate going on...

Okay, now I'm scared. I didn't know mold was that bad! I wish someone would help me out on my other post about UV sterilizers, 'cause the sooner I can order one, the better!

Sorry, I didn't intend to scare you or anything.

It's just that mold SOMETIMES secretes chemicals. It's hard to know if you have the dangerous kind or not, but most types of mold aren't dangerous. They aren't 'good' perse but they aren't bad.

As long as you keep an eye open for new growths, you should be fine.

Don't be sorry. I needed a kick in the pants to really do something about this. I've suspected for a while that we may have a bit of a mold problem in the house, and now I have proof. I think I'll talk to the boyfriend about the idea of getting an air purifier, even though I've already been prodding about an air conditioner for a while, and nothing's come of that yet... Till then, I'll give all the filters a good cleaning and hopefully that will help for now (in addition to the sterilizer I will get soon).

Just purely out of curiosity, if the mold were to make my fish sick, how might that illness manifest? What symptoms might it cause?

Anyone know?

Hm, usually fungal infections are easily fought off by a healthy fish's immune system, so I'm not sure what the result will be.

If someone knows for sure, I'd ben interested in hearing what they have to say too.

Hi starla, have the exact same problem on my filter. and guess what, it's a tetra filter also. is the top part of your filter out of the water ? mine is and it uses a kind of water fall effect when the filtered water goes back into the tank. i have just added a new fluval internal filter to my tank as i am not convinced that the tetra is adequate for my tank.