Have no experience myself.............but googled it for the hell of it.......
came up with this on parrotcichlid.com
Prolapsed Rectum? (Ovipositor) Posted by ParrotCichlidGirl on: Thursday 13 May @ 07:15:17 (Read: 146)
KY writes: "Hello,
I have 2 BP's and the female seems to have what looks like a prolapsed rectum. There is a bubble like skin hanging out of her rectum (butt).
Has anyone seen anything like this and if so, how have you treated it or can you?
Note from ParrotCichlidGirl - this is most likely her ovipositor. She may lay eggs soon, but that doesn't always happen. It doesn't need any treatment - as long as you see her pooping normally. It is close to the rectum but is NOT the same thing.
After many hours looking at this fish last night and getting lots of other info off other forums i still dont know what it is.
It ended up looking like this late last night and today its completely back to normal
Others thought that it might be a calapsed rectum or some sort of worm. I think its something to do with its reproductive organs as the fish has been doing everything that a BP should do during mating.