I have five black mollies, and one male is having some serious issues. I just wanted to check with you guys to find out if something is wrong with him. In the tank I have two females that are just about ready to pop. There is two other male black mollies with him. He is swimming wierd. He will swim straight up and down for about three hours and then swim normal for about ten minutes and then back to the wierd swimming. There is no signs of disease on him or any signs of another fish attacking him. Is he just a wierd fish or is there something wrong with him that I am missing?

Sounds like swim bladder. This is normally a bacterial infection. The infection is normally caused by an increase in decompaosing organic matter. IE. plant wastes. Its best to remove this once a day or once every couple of days. It can be treated by using a bacterial remdy from your fish store, and boosting water quality to optimum levels.

The swim bladder is an organ that helps fish determine the depth at which they want to swim by controlling bouyancy.

What are your current water params? It could be Swimbladder, as Miagi said.

It sounds like you have 3 males and 2 females? It's best to have 2-3 females per male, otherwise the females can get overly harrassed and then possibly abort their fry. More females then males gives each female a little break from the males' attention. But anyway, my point about that is, the other males might be getting aggressive and fighting over the girls, and thus attacking him. You might not see it...but it can happen. :)