Please help! Fin damage...

[nowzem]

Ok, so I bought 2 beautiful males and rec'd them last week. Well one of them just up and died and I still don't know why (I think his tank became contaminated with an unknown substance...). The second one was doing beautifully and low and behold I get up today and his fins are shredded and torn and his dorsal has a big hunk missing. When he arrived from his shipment (in a box for less than 24 hours) he had a little bit of his tail missing, so I suspect he may be a tail biter... my other suspicion is the filter intake. He seems to be fond of hiding near it...so I added some extra plants and he hasn't stayed near the intake (unless he does it at night?). He is a DTHM and he is my very favorite little guy, so please help me. :)

He gets weekly 100% water changes and 50% on my day off.
NH3 0.25 (I know, it's high)
NO2 0.0
NO3 5.0ppm
pH 6.4
well water

Heat 79-81F

The fins don't appear to have any fuzz or slime and he's really active (as can be witnessed by the blurry pics!) He doesn't have any tank mates and the tank is filtered by a whisper internal filter (size appropriate and turned on the lowest setting). He has one plastic plant and some live riccia and cryptocorne in the tank... His appetite is fabulous and he loves to come up to the glass and check me out :)

My questions are: what caused this and what the heck do I do about it? I know I did a big no-no by not cycling his tank before I put him in there but I was hoping extra water changes would make up for it (obviously it isn't..should I increase these to 25%-50% daily?) I've cut the filter off for now...

Thanks in advance!

[nowzem]

PS...he also likes to wedge himself into things...behind the filter, into the cryptocorne.... :)

[nowzem]

No advice for me?

[Oldfishlady]

What size is the tank......

If he is a tail biter....that can really be hard to deal with.....so frustrating.....I would increase the water changes to daily for a few days to prevent any secondary infection, good that you turned off the filter...you may have to leave it off and since you are already doing twice weekly water changes of 100 and 50% each week....I would keep up with that......
You can try dimming the lights, moving things in the tank and out side the tank....try adding live foods, add some tannins from IAL or oak leaf and see if that will help....some are just tail biters and not a lot you can do sadly......

I would remove the plastic plant and the cycle IMO didn't have anything to do with it.......

[nowzem]

Thanks so much! <3. I will try that! He has such a beautiful tail and personality, I wish he wouldn't do that, but maybe his fins really are too heavy (sad).

OH It's a little 3 gal. It was just going to be his QT tank but he WAS doing so well I didn't want to move him...and now with the loss of 2 bettas and another with fin rot (I think it may have been bacterial..but I don't know where it came from yet/maybe just the water?) I'm terrified to move any of my fish when they are doing well.