I have a halfmoon.. err super delta... I paid a HM price for him at Petco though... (still irritated about that can you tell? They wouldn't believe what I was saying, but I still really wanted the little guy so I got him.)
When I got him his ventral fins had a slight curl to them. I put it down to sitting in such a small cup. After owning him for a few months, providing him with silk plants some tannins and driftwood etc. He still has curled ventral fins. In fact they are worse now then they were when I got him. I am guessing this is because he likes to sit on things? More so then my other guys? It's really kind of depressing to see his circular ventrals, like he got them curled with a curling iron. He can't straiten them out at all now. To me it looks like he is bending his elbows- if he had elbows..
I wasn't sure if this could be a genetic defect, or if it is some other problem, or if this is normal for some fish. I can't find anything googling about this so thought I would ask. I can't eliminate hard water but his tank has a lot of tannins plus driftwood in it and none of my other bettas including my CT are having issues.
As soon as I can, I will take new pictures of him to show how bad they have gotten. It might be a bit before I can borrow a camera though.
Thanks in advance if anyone knows