I have 4 male guppies in my 10 gallon along with 5 lamb-chop rasboras (I need to bump up their school, I know. :-?). One of them looks very pregnant. I was certain it was a male, but it has this massive lump on it's belly. I noticed one of the other males harassing it, then all of a sudden it had this massive lump . . . Maybe it's a tumour? I'm lost. I'll post some pics later.