O.K. I received an E-mail to provide more information. I wasn't sure if I should reply to that or respond here, so I'm responding here. Here's the full skinny:
I've had community aquariums in the past. I tried a couple times to introduce a betta, and they always died within days. I chalked it up to too much water commotion and maybe other fish. A couple years ago I yanked out an antique 2-gall fish bowl I've had, bought a half-moon betta, and kept him for almost 2 years. He went too soon, but I think I know what I did wrong then. I think I overtreated the water, did not change 100% of it, maybe did not do enough water changes, and fed freeze-dried food. Live and learn. So then I decided to get a new fish and ditch the bowl in favor of an Eqlipse 3-gallon with a filter and bio-wheel. As soon as I received it in the mail, I hated it. The whole cover has to come off every time you feed. But, I went ahead with my plan, and found a distributor in NYC over the internet. I'm only 350 miles from there. I spent a small fortune on a stunning half-moon. I waited with bated breath for his delivery the next day, and when it came, my excitement went to horror when I opened the box and found TWO male bettas. Seller was trying to be nice. I didn't have the heart to give extra fish to a store to sell to someone who would keep him in a cup. So, I dug out the old bowl, swearing the whole time, and plopped him in. He lived there, and my gorgeous one lived in the Eqlipse, happily for a couple weeks. I then devised a plan to set up a 10-gallon, divided aquarium with a filter I could turn down to 1/2 strength, which I would place right in the middle so no fish got exposed more than the other. I had the aquarium set up on a Tuesday, water went in on Wednesday, filter was turned on Thursday, and Friday night the fish went in. I aged the water ahead of time a day or so, but still put in some Stress Coat. (Chemist/fish enthusiast who works at PetSmart told me to do NOTHING else to the municipal water in this town.) I did put in some aquarium salt, too, and a couple drops of aquari-sol, just for the new set-up. Tank has LED lights that are not too bright (Marineland single-bright). The divider is plastic mesh held in by plastic report binders that I siliconed to the sides. I used pure silicone - no additives. I fed the fish frozen brine shrimp and blood worms and betta pellets, alternately. I kept the temperature between 75 and 78. It would go down a tad overnight and then warm up with the rest of the house during the day. I put no other fish in yet. Four days, everything fine. Day five, one sick fish (acting obviously sick with crappy looking fins). Started adding melafix as directed on the bottle (which I now see here is not correct). Next day, no better. Get paranoid about my water, so I yank them out back into the bowl/Eqlipse situation in nice fresh water. One fish rallies a little. Had to go away for 28 hours. Came back, still bad-looking fish. Immediately have my water tested by PetSmart. Perfect water. No nitrates, chlorine, ammonia, or bad PH (our PH is high at first here, but the water goes a little more acid on it's own - chemist tells me). So I put the fish back in the tank, turned the heat up to 80, added melafix, and didn't turn the lights on except for natural light. Next day, dead $50 fish. "Free" fish is hanging on, but he's been on death watch for 3 days now. He lays on the bottom of the tank, will come up and eat if I roust him, and his fins are practically gone. I stopped adding melafix and put the charcoal back in the filter to get it out of the water. I can't smell it any more. Some sites say absolutely you cannot keep these fish in an aquarium. But I know so many people who have in the past! I am driven to distraction by this. These fish going from gorgeous to (practically) dead in four days! Could this possibly be just from water movement from a filter???? I was going to give them some buddies, but I never got that far. I have read that water fluctuations can give them fin rot, but what does that mean? Two degrees? Or would it be 15 degrees? What is bad fluctuation to a betta? What on earth am I missing here???? I have so much time and money invested in this now, I don't want to forever give up. And they are really the only fish I like because of their personalities. Is there a way I can make this work? Thank you, whoever you are, who stuck with me through all this!!!