Daily water changes, not just for the AQ salt (which you do not want to add more of without a water change because it doesn't evaporate out or, if you have a filter, it doesn't filter out) but also because an unfiltered tank will end up with lower water quality quickly, and for fin rot you want to keep the water clean so that the fins start to heal. Bad water quality is what causes rot most of the time, and the clean water, salt, and stress coat will help the little guy get better. For a healthy fish, the two water changes a week is proper tank maintenance and will help your fish to remain healthy.
I'm not sure about the addition of your live plants, partially because I know that you want to keep the water surface clear for the betta to be able to breathe, and I'm not 100% knowledgeable about live plants and fish. I don't know how either of those two plants will effect the water. I'm sorry, I can't offer you any good advice either way with that. I'll try to find someone who can help though. :)
From what I know in the short time I've had a planted tank, both plants sit on the surface and are really good at absorbing excess ammonia. They're basically weeds under full light, which makes them hardy and easy to grow in low-light conditions. Both have good root systems that grow from the surface of the water and provide structures that bettas like to build bubblenests into.
Is it silly to be worried about waking up the betta to change his water in the dead of night?
The instructions on the AQ salt say 1/2 tsp per gallon, but I recall you want to double that dose for cases like fin rot.
I also have a few gallons of water from a well-cycled tank that I can put into the bowl. That would be the equivalent of adding bacterial supplements to the water, wouldn't it?
Also, thank you so much all for your advice. I had a suspicion something was up, but I've never dealt with a case of fin rot and didn't know what I was looking at.
I would break away from pellets, they never hold enough nutrition for an ill Betta, especially a picky eater. If you can find some frozen, not freezedried foods like GlassWorms (mosquito larva) you can feed him that instead. It's something that will help him greater than any pellets or flakes out there and will entice him to eat. Imagine being handed dry cereal every day and becoming bored with it, then being handed a nice juicy steak (or if you're a vegetarian then a nice big fresh salad).
If he actually is sick and you're treating him with AQS then I wouldn't add any live plants at all. You may want to find him a very soft plastic plant or a silk plant. Having no cover at all can really upset a Betta and make him feel very out in the open which isn't something they like at all.
Since you are doing the salt treatment in a 1 gallon you'll want do do daily water changes. Now for a normal tank of 1 gallon with a healthy fish then it's pretty much every other day.
Sagat, It's not silly to be up in the night worried about the fish and his water. If you've already made a water change today, however, you don't need to make another one until tomorrow. You don't want to do more than the one per day because you don't want to stress the little guy out any more than he already is since he isn't feeling good. And yes, you can do 1 tsp per gallon of water since he's a sick fish. I wouldn't recommend adding a different tank's water to his bowl, especially if there are other fish in the tank, simply because this guy's immune system is already low since he is already sick, and you don't want him to catch anything that may be in the established tank that doesn't effect your healthy fish. It's better to not have the bacteria for the time being because you want the fresh clean water. Just make sure you let new water sit and acclimate for 30-45 minutes before you put him in and make sure you try to have the temperature of the new water as close to the old (preferably the same so as not to stress him out) as possible. If you use a small container to put him in while you change the water, you can float it in the new water, so the temperature is evened out when you move him to the new water (if it will fit in the bowl). If it doesn't fit, I know some people recommend that you add a small amount of the new water every 10-15 minutes until the temperature is the same.
Alex and... I'll call him Mr. Blue for now, are happily sitting in their cups acclimating to their new water. I wanted to play it safe, so I'm going to be adding water to their cups slowly over the course of 1-2 hours before I add them back to their respective tanks.
Alex is the guy we've been talking about and he's in the rightmost cup. Alex got a 100% change, a tsp of AQ salt, ~.5mL of StressCoat+ and will be getting some thawed brine shrimp in his cup before I transfer him over.
Mr. Blue got a 50% change and ~.5mL of StressCoat+ and was fed beforehand, but will probably get one or two thawed shrimps, just as a treat.
Awww, poor Alex! He is so small. He's lucky that he went home with someone who cared enough to take extra care of him!
Everything you're doing is great! Remember when you feed him, he may not eat at first. Just take one shrimp and slowly pull it across the water in front of him. Bettas are natural carnivorous hunters, and the movement will help spark that in him. Try for a few minutes, and if he doesn't go after it, go ahead and try again in a little while. Keep trying till he eats, and when he does, feed him a few. You don't want to feed him too much, because remember, his stomach is small (a betta's stomach is about the size of his -healthy- eye).
You did absolutely perfect with the water changes, and you are acclimating them very well. And I'm sure that Mr. Blue will love a Frozen Shrimp Treat. :)
Boy, it was hard to find time to get some good pictures between all of the stuff going on in the house, but here's an update:
It took awhile to get Alex to eat, but I finally got him to recognize brine shrimp as food. I used a medicine dropper and slowly dropped brine shrimp in front of his mouth over the course of about 30m. It took about 8-10 tries, but he finally got the idea they might be food and ate one. I probably overfed him too much (4 or 5 brine shrimps of varying sizes), but I was happy he ate.
After feeding him, I put him in the living room on a table where my old betta tank used to be. I'd built home-made ductwork out of a cardboard box so that I could redirect warm air from the vent onto the top of the table, which bumped the tank temp from 72F to 80F... Then realized I had no reliable way of matching water temp.
So, on the 1st, I took my old minibow1 out, filled it up with treated water and set it next to Alex's tank so that that the water could be heated to the same temperature.
Feeding went waaaay easier this time and Alex's behavior had perked up alot. He was acting like a normal betta and he didn't swim like he was fighting his water tension or his own buoyancy and only one shrimp hit the bottom of the tank during feeding time; better yet, he actually had the energy to pick the one fallen shrimp off the floor of the tank.
Evening feeding went even better, since I noticed he'd either started blowing bubbles or was attempting to build a bubblenest. His fins aren't ringed in black anymore -- It's more like a ring of smudge, but you can see it for yourself in the picture.
I decided to keep him with us til my son goes back to daycare/pre-school on the 7th, so that should give him another 5 days of recovery and I'm testing out my 7.5W heater in my minibow1 to see how hot it makes the tank. If it's in tolerable limits, I'll offer it to the teacher to help keep Alex warm.
Over the weekend, I'm going to start transitioning him back to pellets, to make sure he continues to eat after he leaves my care.