Top pic is Male on left female on right.
Notice the narrow arch on the males abdomen tail and the female has a wider skirt and bigger swimmerettes.
Can't see the other two pics very well. A female will have a saddle on top of shell at the body, and will be a lighter color sort of orange. Males may start fluttering around her. They seem a little small, just look for the saddle.
And deep up on regular water changes.
If you have an I take for the filter, make sure it has a pre filter sponge on it so nanies dont get sucked in.