I have had this betta for about two years now, since he was a baby. A couple of months ago he started having trouble swimming. He would swim upwards, but could not stay there - instead, he would sink back down - tail first.
Water tests were normal - I only use the API liquid chemical tests, not the strips.
Our first impression was SBD. We control feeding pretty well (not the only betta I have), but I figured each fish is different, so put him on a pea/fasting diet. This did not help. Next, we tried some medicines, but that did not help either.
At this point, I just think this fish just might be disabled, but I feel a little sad watching him struggle to stay afloat.
Any ideas on what it could be - other than SBD, or what else I could try?