don't be frustrated. these things happen. same floating problem happened to one of my bichirs that i had for couple years. couldn't figure out why. and then i had a few bichirs (all small except for one) that developed some balance problem seemingly out of the blue, they couldn't stay upright, would struggle to swim, sometimes swimming in spiral. these didn't have floating problem though. anyway, nothing i did was able to save them, and i couldn't explain what happened.