Whats Up With My Bettas Fins?

It's a long story, really. It begins last February, when I bought my betta. He had beautiful long fins. Back in September, his fins looked like this:



However, I thought his fins had gone down in size and become a bit tatty, so I bought him a brand new setup in october as I blamed the ceramic media in his old biorb tank for the damage.
At the end of December, his fins looked like this:



Then there's the picture in my DP which I took a few months ago - completely different right?

Today I took this picture:



What's going on with his fins? They just seem to be dissapearing for no apparent reason, and then almost changing shape. I'm pretty sure it's not fin rot, (no black edges etc) and water quality is usually fairly good with weekly w/cs of 30% or so. Nitrate levels aren't too low though as I have a fair quantity in my water supply.

Any thoughts?

Many Thanks

Bless him.
Could it be;
Fungal infection (which rots the fin more evenly and is more likely to produce a white 'edge')

Thanks for the reply. Unfortunately, there doesn't seem to be any sort of coloured 'edge' to the fins at all though - they just appear to be dissapearing without other symptoms that I know of. I haven't spotted him tail-biting either and he eats well enough too. Any other ideas?

pablothebetta said:

Thanks for the reply. Unfortunately, there doesn't seem to be any sort of coloured 'edge' to the fins at all though - they just appear to be dissapearing without other symptoms that I know of. I haven't spotted him tail-biting either and he eats well enough too. Any other ideas?

Click to expand...

Maybe he is cutting them on something, or his tail got sucked into the filter and it started to rip?
Btw does he have any tank mates? Or the water might be too acidy, like a Ph of 5.7 or something?

sona98765 said:

Maybe he is cutting them on something, or his tail got sucked into the filter and it started to rip?
Btw does he have any tank mates? Or the water might be too acidy, like a Ph of 5.7 or something?

Click to expand...

Thanks for replying. Never noticed him being sucked into the filter, I think it's a fairly gentle flow. He has some C.Pygmaeus in with him, though I wouldn't think they were too nippy. There's also some shrimp & snails, but I can't think how they'd be the issue. Not sure of pH, think it's around 7 from what I remember from my last test

sona98765 said:

Maybe he is cutting them on something, or his tail got sucked into the filter and it started to rip?
Btw does he have any tank mates? Or the water might be too acidy, like a Ph of 5.7 or something?

Click to expand...

Thanks for replying. Never noticed him being sucked into the filter, I think it's a fairly gentle flow. He has some C.Pygmaeus in with him, though I wouldn't think they were too nippy. There's also some shrimp & snails, but I can't think how they'd be the issue. Not sure of pH, think it's around 7 from what I remember from my last test

Bump

Wish i could help, but ran out of ideas!
If i was in your shoes id keep up with the water changes and add aquarium salt for good luck! (thats if the salts ok for the other species)

Could be biting his own tail but judging from the pictures it doesn't look like it to me

Thanks for replying. It really is quite strange, I just hope his fins don't continue to dissapear