sexing 3 spot gold gouramis is done by the shape of the dorsal fin alone. body shape is applicable when sexing GIANTgouramis when they mature but isnt accurate in smaller species. ie: some folks overfeed which makes everybody female. see where i'm goin' w/ this? males when adult will display a much longer dorsal that will taper off towards the tail (some will even reach it) and end in a distinctly sharp point. female dorsals never reach the tail and are rounded off. remember you're looking at the rear end of the dorsal, not the top of it. if your fish is an adult it's easy.
How do you tell?? (Might as well add to this) What about a female betta?? I may have a little problem. I like female bettas as you do, Joel, but yesterday the three that were available were very colorful - more so than usual and one of them had a lot more finnage. They weren't exactly small either so I didn't consider them juvies. Then I got to thinking. I have a dark red male (supposedly) that I have had for months. He has a very short round tail and it is not because of damage. I really don't want to test this out by putting a female in with him/her. On the other hand, if he was a she, I could maybe put her in the tank with the other females and get another male. I have noticed that some females, in spite of their color have a darker stripe on their side, but that isn't consistently true either.