How can you TELL if the FISH is MALE or FEMALE?!?!

Sword tails are easy to tell male from female. The long sword tells everyone quickly that the fish is a male. Live bearers are all easy to identify. I think you must have egg layers.

I have guppies at home. It's easy to tell which is male and which is a female. A male guppy is smaller, but it is colorful and it has a beautiful long large tail and it's like a beautiful skirt. Whereas a female guppy is bigger with a big belly. It's not very colorful. I love China

It depends on the type of fish. Livebearers like guppies, platies, mollies, etc. it's pretty easy-you look for the gonopodium in the males-the tube shaped appendage on their belly just before the tail. Females will have a triangle shaped fin in that area. With other species, again it just depends, but usually females have a more rounded appearance, and males a more stream lined/thin appearance. And, not always but some species, males usually have more coloring then females-like gouramis. Some species of cichlids you can use the "venting" method, which can be difficult if you don't know what you're doing. Basically, looking closely at the vent area for a V shape or a U shape to distinguish male from female.