actually just started my first aerogarden grow myself, about two weeks ago. The little guys are looking pretty, and are smelling the place up! Good shit.
But to answer your question, I am just using the stock nutrient right now and the plants like it. The space they are in is slightly cool, as the crawlspace is in between the heated house and the cold outside, but it seems to be keeping the liquid cool enough to discourage any root rot. That all being said, I'm not sure that the aerogarden will be big enough to keep the plants in the entire lifespan, and I know that the light on top will not be enough, so I am planning on transplanting them to a larger container in about two weeks and I have a mad scientist experimental grow light in my head that I am going to try out.
Good luck!