I've got an angelfish (pterophyllum scalare) who doesn't look very happy
right now: damaged fins with bloody streaks on them and around the body (at
the base of the fins), black specks (seems like Ick, but black), and the
fish seems very thin, being very small in comparison to the second angelfish
in the aquarium, which was purchased at the same time and which,
surprisingly, is very healthy.
It's a 50g aquarium, pH=7,1, slightly hard water, filtered over peat, no
ammonia nor nitrites, ~15g water change/2weeks.
Does anybody have any idea what could cause this?