Its been years, but freshwater was always my choice. I succeeded in hybridizing a big 3 inch long female Gambusia with a snakeskin endler's livebearer, and resulted in even BIGGER "guppies" with fucked up weird colors. I learned later that this was actually a huge accomplishment, and I wish to this day I kept their bloodline going. All of them were able to breed, too. I thought they'd be sterile Today i just have a small 10 gallon tank with a single crayfish, the only remnant of a breeding population I tried to start for easy live bait.. I should take some video, he's a vicious fucker, rushes right to your hand and will immediately start trying to eat you.
Just to let you know there's an aquarium thread 180 pages long here http://forum.grasscity.com/general/814191-anyone-else-have-aquarium.html