A week ago I had a loach pass away, but I presumed that was from lack of food. I wasn't feeding them nearly as much as they needed. He had no physical injuries and never swam strangely.
Yesterday I had a rasbora finally pass away. We named it gimpy because it always swam funny and was picked on by the others. But yesterday it had a slightly curved spine. I took it out and it died a few hours later. It had no wounds or spots on it's flesh.
Now today my betta has a giant spot on his side that's rather huge for just appearing. It looks like a fungus but with the other deaths im not sure. He still wants to eat, but can't use that fin so he doesn't like to swim much. I plan to set up a quarantine tank for him shortly.
My ammonia levels are between 0 and .25ppm so I'm going to do a large water change to get those levels down.
In the meantime, any ideas of what would cause this and what it means for my remaining schools of rasboras and loaches? And my shrimp too... Everyone is doing well at the moment. There is nothing strange in my aquarium.
Also, for treatment for the betta I have aquarium salt and also a jungle brand antibacteria/antifungal tablet treatment. I will be going to the pet store regardless today, so I would be able to pick up something else if need be.
38 gallon tank with sand and gravel substrate, driftwood, some dwarf hair grass, wisteria, java fern, and watersprite. There are 7 loaches and 10 rasboras, as well as maybe 7 ghost shrimp. The temp is at 78degrees. I have an Aquaclear 50 running.
Thank you for any help!