Venting works the best, also females tend to have a more rounded forehead slope and males have more of a sharp angle. Color in males is usually brighter in the fins and tail than females but it's not always like that. I have grow out pics in my gallery of my females and male if you want to compare. My male was about 3 inches when I bought him and is now about 6-7 inches. The female with the babies is about 3 1/2 inches the other is 4 inches. On my male the vent is tight and pointy and the females have a plump bubble look.