Fish tank mold?

[BullTerrierChild9]

Hi, My family member's tank has odd white specs that resemble mold on his tank.
Lately, the fins on his fish have grown shorter and more tattered, and one even passed away. At first, we thought that it could've been his pufferfish but they don't seem to show aggression towards the other fish (based only what we have seen), but we will keep an eye out nevertheless. I am wondering, however, if this odd growth is causing the fish harm, promoting fin rot, etc. Is this bacteria or just algae (there is also normal green algae growth on his tank that looks much different)?
Thank you in advance!

 

[GaryE29 144]

This appears like something related to overfeeding (large scale) and not water changing enough. It could be Epistylis, although the pattern and shape is different enough it probably isn't all that creature. There's nothing to say several organisms wouldn't be at work though.

If this happened here:
step 1: I'd clean the glass.
step 2: as I cleaned I would siphon out at least half the water.
Step 3: I'd replace it with water treated for chloramines or chlorine, depending on what you have.

Over 2 weeks (minimum) I'd repeat those steps several times.

And now, the hard part. I would look at feeding, and reduce what's going in by 75%, to pick a number. I'd rinse out filters, and see how the lighter feeding goes. I'd probably feed that 25% portion only 3 or 4 days a week.

Those white pattern things used to be very common in the hobby in the era when we simplistically thought we could have balanced tanks with no water changes. They're harmless, though fuzzy white spots on the glass may not be. They were usually seen as a sign of impending trouble. I'd agree with that view.

 

[BullTerrierChild9]

This appears like something related to overfeeding (large scale) and not water changing enough. It could be Epistylis, although the pattern and shape is different enough it probably isn't all that creature. There's nothing to say several organisms wouldn't be at work though.

If this happened here:
step 1: I'd clean the glass.
step 2: as I cleaned I would siphon out at least half the water.
Step 3: I'd replace it with water treated for chloramines or chlorine, depending on what you have.

Over 2 weeks (minimum) I'd repeat those steps several times.

And now, the hard part. I would look at feeding, and reduce what's going in by 75%, to pick a number. I'd rinse out filters, and see how the lighter feeding goes. I'd probably feed that 25% portion only 3 or 4 days a week.

Those white pattern things used to be very common in the hobby in the era when we simplistically thought we could have balanced tanks with no water changes. They're harmless, though fuzzy white spots on the glass may not be. They were usually seen as a sign of impending trouble. I'd agree with that view.

Thank you! Do you think it could be causing the deterioration of the fish's fins?

 

[GaryE29 144]

It could be a symptom of declining water quality, which could help micro-organisms that could eat at fins overpopulate. You want good bacteria and archaea, but there are a lot of things that you can'cultivate' by mistake.

I'm old enough to have seen the no water change era, and fin fungus issues were chronic back then. Since I was a kid, I tended to overfeed too.