I have 2 10 gallon tanks, both have filters, heaters, & live plants, as well as a couple ornaments that provide hiding places. Last thursday I purchased two spotted cory's (one for each tank). By friday night my catfish in tank #1 was dead & my betta's tail looked like it was getting nipped. Saturday morning the catfish in tank #2 was missing, literally no where to be found. Saturday afternoon my betta in tank #1 had a white spot by its mouth and his tails were turning black. Later that day my betta took a turn for the worse and i quarantined him after reading on here that I should do that. Sunday morning my betta was dead & the Betta in tank #2 had a white spot on its head, the catfish also turned up dead. I have my second betta quarantined & for the past two days he will not eat. The white spot has gotten a lot bigger and now parts of his tails look funny, they aren't rotting away, but they almost look like they have growths on them. I have been treating the water with something called Betta Revive and its supposed to treat for bacterial or fungal illnesses, but I see no improvement. Any suggestions? I really do not want to lose this betta after just losing my other one. Also none of my other fish have been affected. And my other two catfish are fine.
Sounds like a fungal infection to me as the symptoms match yours
White, or fuzzy growths on the outside of fish
Fish has become less active
Patches of white
This disease is very common with stressed fish and is cured with Higher levels of added salt, easing the temperature within the tank to 80 will also help as it will speed up the life cycle of the disease. If the disease progresses then invest in a high quality fungus treatment to help aid the treatment, if that doesn't work then I highly suggest that you either euthanize the fish or heavily Medicate, sterilize, and heat the temp even higher within the tank
There are many factors to what causes this specific disease but it's similar to many others.
-poor water quality, like high ammonia, and nitrites along with unecxeptable Amounts of nitrates
-stressful tankmates and constant nipping
-being battered around by flow
-not acclimated properly
Are all main factors to the disease as they all lead to a lored immune system which leaves all fish helpless towards all diseases
Upon further inspections on the picture it seems to be a wound of some sort. DO you have any sharp or recently added decorations within the tank itself? If you do then that is most likely the cause of the wound. if it really is fungus then just adding a treatment won't do as much as it guarantees in that short amount of time. Ideally you should save the treatment until it is dire, usually it clears up after salt treatments, heat, and salt baths. I wouldnt recommend any of those unless you are sure that it really is a disease as they do cause stress in the fish in very specific ways it still help treat diseases
No sharp objects, the wound appeared after i had introduced a new spotted cory, and the cory died a day later. I have checked my levels over and over and everything is normal. His tails now are also ratty looking more pics to come soon.
It seems as if you have plastic plants contained in the tank which are notorious for ripping fins, and leaving them in an unacceptable conditions which look rather unsightly. So in your situation I don't see any problems unless the fins have a black edging or fuzzy edging
To the real question, from not properly quarantining your fish they could have easily have introduced something into the tank but still typically your fish shouldn't get theses diseases unless it's immune system is low, for now you should just
-maintain water parameters and test the water daily, doing 25-50% water changes daily or every other day
-raise the temperature to 80 as this will speed up the life cycle of the disease and it will go away faster
-take precautions and start a low dose of salt, of it doesn't seem to affect the fish negatively then raise it to a full dose
- if these precautions to eliminate the disease don't work them you should add a high quality treatment but if you wanted to you could just add it during or before you take the previous suggested treatments