Hi there. I am new membership here. I am profound deaf which I am not really good English Grammar ok..

I have new guppy fry about 20. Also few adult male and female...

I have noticed some of them have fin (back of fish) fall off or rot. Is that normal as like human hair to cut off??

Hope hear from you.

Thanks.

It's not normal. Either other fish are nipping them or it's fin rot that need treating

__________________

Unfortunately fins don't just fall off by themselves, it's either the case of physical damage (sharp decor, fin nipping etc), infection (e.g. fin rot) or a genetic defect (untreatable, and in which case the fry should be euthanized immediately).

I'd suggest testing your water for pH, ammonia, nitrite and nitrate. If an infection such as fin rot is indeed to blame, then the underlying cause is nearly always inadequate water conditions. Poor water quality is a major constituent of stress, which in turn results in low immune systems and high susceptibility to disease. Fin rot may give rise to other problems such as fungus which feeds on the dead tissue.

If we can eliminate possible causes, we can find the real culprit. In the meantime, I'd like to suggest (if possible) quarantining the affected fish.