Angelfish - white dots that make pieces of fin fall off

[CalmedByFish]

Can't get a good picture, but can give a good description:

1 angelfish in a lightly planted 55 gallon. Only tank mates are snails.

Every few months, 1 tiny white 3D dot will appear on a boney part of a fin - not the webbed part. The dot tends to be about 1 cm from the tip. After days to weeks, the bone is bent at the dot, as if broken. A few days later, the dot and the boney section past it simply fall off. The most frequent fins are the 2 long dangly ventral fins.

Currently, there are 3 of these white dots - 1 on a ventral, and 2 on the tips of the anal fin. This has been happening for years, but I'd never seen 3 at a time before. 

Parameters:

• pH 7.8-8.0
• Nitrates 10-30
• Hardness 11
• Nitrite 0
• Ammonia 0
• KH/Buffer 3
• Water Temperature 76

Any ideas?

[Colu]

 it possible it's damaging it fins on something in the tank

[CalmedByFish]

16 minutes ago, Colu said:

 it possible it's damaging it fins on something in the tank

I wondered about that. In the past, I did have plastic plants in the tank. But in the last few months, the sharpest thing would just be the gravel, and he usually doesn't swim low enough to touch it. I think it's unlikely that the most recent white dots are the result of injury.

And even if they were the result of injury, what exactly would the white dots be made of? Something like a scar? A speck of fungus, but not a type that spreads? I'm baffled.

[Colu]

On 5/14/2021 at 7:03 PM, CalmedByFish said:

I wondered about that. In the past, I did have plastic plants in the tank. But in the last few months, the sharpest thing would just be the gravel, and he usually doesn't swim low enough to touch it. I think it's unlikely that the most recent white dots are the result of injury.

And even if they were the result of injury, what exactly would the white dots be made of? Something like a scar? A speck of fungus, but not a type that spreads? I'm baffled.

It's a  difficult one if you can get a picture that would be helpful in diagnosing your fish

Edited May 16, 2021 by Colu