Need some help!

[jacki89]

So I am watching a family friends 3 bettas while they are on vacation. I went to feed them tonight and I noticed one of the crowntals has this big red ball on part of his tail--it almost looks like a blister and it's very red. If anyone knows what it might be I would love some advice just to pass back to them..they are new fish owners. Here's a link to the pic a took: http://i17.photobucket.com/albums/b7...s/DSC00032.jpg. Let me know if that works

[Sasami]

It might be some sort of infection but it'd be great if you could give a bit more info . Does he have any other symptoms? How old is he? What sort of tank set-up is he in?

No matter what it is, I would start by doing a water change and getting the water tested (most pet stores will test a water sample for free).