I got a new Betta about 3 weeks ago. He was a happy, healthy fish until two days after the first water change. He started having trouble swimming, then floated to the surface and rolled onto this his side. I wasn't overfeeding and used treated water.
This cycle has now happened three times...seems sick, change water, gets happier, then about 48 hours later back to swimming funny and floating to the surface. I have been reading about pH and know I could do better with the water balance, but why would a water change help, but only for a short time? Betta experts...help!