Shredded looking tail not improving

[LexHarr]

Alright so around two weeks ago, I noticed that my fish's tail started to look raggedy and split. I thought it was because of the plastic plant I had in his tank and I was planning on buying him a new one, even though he's been living with the plastic one fine for probably about a year now.

It kept getting worse by the day, though, and I realized it looked like fin rot (with darker edges and everything). I started treating him with API Tetracycline. It seemed to be working and I changed the plant anyway for good measure. It was working after a few doses and I could see new growth on his tail.

I went away this went away this weekend and came back today and his tail has a bunch of new tears. I really don't know what to do at this point since there's nothing in his tank that could be hurting him and before I left, he was improving.
Should I continue the tetracycline doses? Or use aquarium salt or something else? I'm still pretty sure that it's fin rot, but shouldn't it be gone by now?
Please help :( his veil tail is starting to look like a crown tail

[callistra]

Tetracycline is not a very effective drug and it's really harsh on fish.

Please fill this out so we can get a better idea: http://www.bettafish.com/showthread.php?t=49233

[LexHarr]

I have a 3.5 gallon tank with a filter, no heater, no other fish.
I feed him two betta pellets a day and I usually give him blood worms or brine shrimp once a week instead of the pellets.
I do 50% water changes once a week and I use API stress coat to dechlorinate the water.
He's acting completely fine, lively and has an appetite as usual and he looks fine minus his tail. As I said I noticed approximately two weeks ago and started treatment with the tetracycline a few days later. He's about 3 years old now and the only time he had something like this was a year ago, but the tail splitting was due to a sharp plant and he got better after I exchanged it for something softer.
And I haven't tested the water

[callistra]

Fin rot is usually caused by poor water quality, and I can tell based on what you have said this applies to you.

It is very hard to maintain a biological filter in something of this size. Many people will tell you not to even try and you will always need twice weekly water changes of 50% and 100%. You can try but you should not do so without a good reliable drops kit. Cycling can take up to two months, during which time you should be testing daily for ammonia and nitrite and doing an extra 50% change anytime either show up. First you would see an ammonia spike, then nitrite. Ammonia will hopefully eventually stick at 0 even after a full week, followed by nitrite. At this point you will be left with only nitrates that can be kept <20ppm by twice weekly 50% changes with siphon/turkey baster or stir/dip method to clean the gravel of debris - never just take off the top.

Also since you have added tetracycline to his tank you have completely toasted any biofilter you may have started to build. You will need to start all over once he is well.

However, a betta cannot heal in a cycling tank so you need to increase your water changes to 50% every other day and 100% weekly while he is healing. I would also treat with aquarium salt at 1 tsp per gallon preidissolved for 10 days. Stress coat at 1 ml per 1 gallon and/or fresh water vitachem at 2 drops per gallon will help with regrowth.

[LexHarr]

thank you so much! I didn't know that the tetracycline was so harmful!