I just got a 55 gallon tank from my brother. We removed most of the water, and moved it here.
The next day all the little fish in it died. The swordtails remained and the two catfish. One of the catfish died too a few days later.
After a couple days we went and bought some silver mollies . They died the the next day.
I went back to pets mart and they said others were complaining about the silver mollies dying.
Next we got some tetras and platies and black mollies.
The female swordtail got cotton spots on her and died. I looked it up and thought it was cotton disease. I treated the tank with medication. Now the male has it. Then all the fish starting getting swim bladder.
I fed them peas and that part went away. Then a black molly turned silver and died. Eyes clouded.
I thought, ICK. Treated tank. All fish now are doing great, BUT the swordtail. He still has the cotton stuff on his mouth, he will not eat. He has skin flaking off.
My water is all safe, except that it is hard. Some nitrate but in safe area.
I have put in a new filter after using medications. He has not eaten in a week and has been hiding in the log. He came out yesterday finally but is still not eating. I do not know what else to do.
I am doing a weekly 25 percent water change. We have a hot magnum water filter. that is very powerful. Now on one note , his fins were looking kinda green spots, but that has healed.
The only thing I have not checked is ammonia, I have nothing to check it with and this point out of money for this week on buying so much fish stuff, but it was ammonia, I would think others would be sick too.
Only thing new, I bought a new heater. The one my brother had was broke and water was to cold.
Now water is at 80. Should I lower it a bit, and can the tetras handle that?