Caudal Blister

[JustKia]

Fish: Male mustard-gas betta approx 9-12months old.

A full description of the fishes symptoms.
Where the caudal fin joins the body there appears to be some sort of blister within the caudal fin. The portion of fin that extends from the "blister" has now gone so he has a "V" missing. The ends of the caudal fin are not bloody or red.
Imagi shows no other signs of illness. He eats well, swims normally, doesn't have any bouyancy or manouvering problems.

Water parameters. (ammonia, nitrate, nitrite, PH, temp', Hardness etc)
Ammonia-0; Nitrite-0; Nitrate~10; pH~7.4; Our water is genreally hard but with little carbonate buffering.

How often you do water changes and how much. Tank size & Filtration
Approx every 14 days about 25-30%.
125L tank divided; filtered by an Eheim 2224 with lots of live plants.

Any chemicals and treatments you add to the water.
Tetra Pond Aquasafe at every water change.
Because my initial thought had been fin-rot I treated with a 5-day course of Myxazin, which did absolutely nothing.

What tank mates are in the tank.
2 other male bettas in their own divided sections.
No recent additions, all three fish arrived and have been together since November.

 

[Haych]

is it like a watery blister or could it be where he caught himself? (kinda scabby)

 

[Honeythorn]

It's kind of hard to tell. A better picture is needed to show it more clearly.

 

[silverrabbit]

My eyesight's not great at this time of day lol, is the blister the white patch? Does it look fluffy at all, or red in the centre? I don't really know what to offer help-wise, but a clearer pic would be very helpful

 

[JustKia]

His "normal" finage is semi transparent, not clear but not really soild.
The area where the "blister" is is completely opaque. It looks kind of puffy in the same way as a small pillow.
There is no external wound, no fluff, no redness.

I'll keep trying to get a better pic.
When their lights come on later this afternoon, I'll get him into a tub and see if that makes is easier to get a better pic.

 

[WILDER]

I think I would issolate the fish and use a bacterial med.