I recently became interested in raising fish so I bought a 10 gallon tank for my room. I bought some random fish to start off with. One fantail, one dalmation molly, a pair of little 26 cent goldfish ( about 1" long), and I bought this pair of golfish that looks like the little ones but were $6 dollars each and are about 5" long. I was looking at them today wondering if there was any way to tell the difference between male and female between either of the pair. I noticed right infront of the back fin on one of the larger goldfish there is a small bump you can barly see. Is this a sign of a male or female? The other one doesnt seem to have this bump. Is there any other way to tell if they are male or female? Also if so how often do they spawn? If I can get these to breed I would buy a couple more tanks and raise freshwater fish to start with. Any help with these questions?