Just a few updates for you guys :)
I upgraded Nixon from a .75 gallon to a Tetra 1.5 gallon with filter/light etc.. it's a pretty common tank from Walmart. I just discarded the filter because a filter in a 1.5 doesn't do much. I wish I could have got him something a little bigger but, no room unfortunately and he was kind of a "surprise." I did add a small live plant, which he LOVES. He hides in it a lot.
Nikki is still doing great in her 3 gallon and she loves the java fern, always swimming around in it.
Lorenzo and Marc are still getting along fine in the divided/cycled 5.5 gallon, so far so good. Haven't had any problems with either jumping *knock on wood* even though it'd be a very high jump. They also have some new live plants that they are enjoying. :)