Thanks for the response =)
The danios have never messed with the bettas to my knowledge. It is a very heavily planted tank. I use liquid testing kits from API. None of the other fish are showing signs of anything, though there was on that looked 'bloated' but pooped normally and the conclusions was that she had eggs since she never seemed sick. The sick betta in questions had clear, stringy whitish poop always hanging out of her but that seems to be getting better after medicated food with metrodanzole. She's currently in a partially filled 4 gallon QT tank next to my monitor with an airstone. The temp stays at around 82 this time of year but I do have another heater if the QT needs it. I put some aquarium salt, 1 tsp per gallon in there with her.
She is no longer clamping her fins and did eat a pellet (but didn't seem happy about it). so symptoms are now missing tail and that odd shiny stuff on her fins. She's eaten brine shrimp eagerly through all this. Even if I don't treat specifically for this shiny coating on her tail and dorsal fin-- do you have any idea what it is for future reference?
And out of curiosity do you know how dangerous using the saltwater version of maracyn would be to freshwater fish (again, for future reference since she does seem to be doing better now)?
Thanks again =) I do like the cup idea.