I'm in a sticky situations. I have a divided 5 gallon, filtered and heated tank with two male bettas. At first it was only home to one betta, but I had bought a new one at the store and had it temporarily in a small tank on my desk until my other heater would arrive. It took too long for the heater to come, and my happy active new betta suddenly became a bit lethargic (after two weeks). I though it was the cold, so divided the five gallons three days ago.
Turns out, the new betta has ick/ich and was becoming more lethargic, so I turned up the heater slowly yesterday until I got to 89F to kill off the ick.
Today the white betta is super lethargic, still has the ick, and now his fins are rotting away.
I'm worried for my older betta. Today my heater is finally coming so I'm separating the healthy boy into a three gallon and going to look for methylene blue to prevent anything he might have caught.
What can I do about the new betta? If he dies, how can I disinfect the aquarium/gravel/filter/heater/decorations?