When we bought Archipelago and Skerries, I noticed that Archi COULDN'T quite sink. The top of her head was constantly sticking out of the water. She could swim downwards for food, but she'd float right back to the top as soon as she'd stop swimming. She was also lethargic. Her water was dingy yellow from waste.
I put her on some pellets, and freeze dried bloodworms, cleaned her cup daily (she was in the cup so she wouldn't lose her food) and within about 3-4 days, she was acting and swimming normally, and now, 2 weeks later, you can't tell that she was ever sick.
Does anyone have an idea of what would cause swimming issues in a baby betta, but is apparently easy to cure? I'd like to know what was wrong in case it ever happens again.