I've been buying ottos for 7 months now and have gone thru about 25 of them . I have three tanks, all pretty close in their chemistry. I've bought them from atleast 4 different places. I acclimate them longer than any other fish I have. They seem to last a month or two then die. I lose no other fish in this time. I've read this happens to alot of people, but can't find why or how to deal with it?