Hi everyone,
Reaching out because one of our adult male guppies has developed a strange red spot on the tail (He has no red coloring normally).
A few months ago, after bringing the tank home from school when my school shut down for CoVid, we had a different guppy (adult male, same basic coloring/type) that also developed a red spot and quickly passed. At the time, we thought it was in part due to the relocation, the poor water quality (I was uninformed and an idiot... I've since learned) and the fact that the adult females we had at the time had just given birth and WAY over-populated the tank.
We've since re-homed the adult females and the babies, and moved the males into a new tank, with clean gravel, updated the filter, and gotten a heater that actually works, and the tank has been fully cycled for months (since we made all of those changes). The most recent change was the addition of some new fish almost 2 months ago (they were Qt'ed by our LFS for us and none have shown any signs of any diseases, and we medicated the tank).
We had no problems until yesterday when this poor guy started hiding a lot and we spotted that spot on his tail.
Tank stats:
15 gallon
5 Adult Male Guppies
12 Neon Green Tetras (We should be around 80% capacity according to the calculation website I used that showed up as a recommendation on this page at some point).
Vallisneria, Cryptocoryne Parva, Java Moss, and Java Fern for live plants.
Plenty of space for fish to hide when needed
No Ammonia according to the test kit
No/low Nitrites/Nitrates (hard to read my scribbled notes)
Ph 8.4
The males, rarely, if ever fight, and this one doesn't ever even play rough (I've called him the mature one, since he doesn't get involved in petty fish squabbles).
Current guess is some form of Fin Rot, we have some antibiotics that we can use to treat that, but we're hoping someone can either confirm, or inform us of what it actually is.
