How to maintain the "hospital tank"?

[willabean]

Hello all.
I have had my beloved little Fish Perry for almost two yrs. For most of that time he has had some degree of fin damage. I had pretty much come to believe that it was from him biting himself, as I witness him doing this on one occasion, but It recently got much worse and I noticed a little raggedy edge to the cute , clear fin beside his face ( surely he couldn't have bitten that?? ). Soooo... After the salt treatments failed, I moved him to his old five gallon with no gravel. Just his log and two silk plants( all cleaned w very hot water ). No filter because his poor tail is so short and tattered that its hard for him to swim. I am treating him with tetracycline, per the instructions on the box. Water heater set at 80 degrees.
So two questions. First, how do I maintain the five gallon with no filter? Must I remove him from tank each week for 100 % water changes? Won't this stress him too much?
Second, what did I do wrong in the first place? Why does he keep getting this rot??
He is ( was ) in a ten gallon heated, filtered tank. Alone. Gravel, castle, cave, 4 silk plants and floating log. Heater set to 79 degrees.
I do 50-75% water changes every single week. I feed him 2-3 hikari pellets twice daily w occasional blood worms. I do vacuum the gravel when I change water. The little testing strips said that my tank was cycled, but I'm starting to wonder if they are accurate. They are very hard to read.
Could he filter be too strong for him? Stressing him out?
If I put him in a 20 gallon can I cycle the tank with him in it? Do I HAVE to cycle it? If I have one betta in a 20 gallon tank w filter, would I Have to do 100% water changes? I want to avoid taking him out of his tank.
Sorry to ramble. My friends think I nuts, but I am devoted to my little pet, and I want him to thrive. How??????

[callistra]

50% and 100% weekly changes in the 5g

The 50% change you can leave him in. Get a turkey baster to remove as much debris from the gravel as possible then scoop water off the top. Make sure the new water matches the same water as is in the tank by using your thermometer under the running tap. Then you must premix up this water with conditioner before using it. I use gallon water jugs you can buy at the grocery store.

The 100% he will need to be removed. Scoop him up in a plastic solo type cup (not net) and set aside while you rinse out the tank. Use same temp water as before. Only this time float him in the tank for an hour after and add just a couple tablespoons of new tank water to his cup every 10 min.

You should cycle the 20g. It would be silly not to. Here's a guide on cycling: http://www.bettafish.com/showthread.php?t=47838 Strips are notoriously inaccurate. I would get a reliable drops kit.

He should not be used to cycle the tank until he is well... tetracycline will not likely work but you can try.

[willabean]

thank you for that info. If you do not think the tetracycline will work, is there something else that you think will be more effective?

[callistra]

Well there's no replacing clean water. Poor water quality is almost always the cause of fin rot in bettas. On top of, if you wanted an antibiotic to try I'd go with Kanaplex, Triple Sulfa or Furan 2 for at least one full week.

[willabean]

Yes, I keep hearing that poor water quality is the cause. That is incredibly frustrating because as Ive said, I religiously perform 50-75% water changes with gravel vac every week. I was under the impression that this was more than sufficient on a 10 gallon filtered tank with one small fish. My goal was to avoid 100% water changes so he wouldn't have to be removed. I was also told never do 100% cleans because this "upsets the cycle".
I hate to be winey, but it seems really difficult to get this right. I love my fish and I'm determined to do right by him, but honestly, I would never get another. Caring for this fish properly is more difficult than my horses. At least mucking out stalls is pretty straight forward! :c
Thanks though.