I've finally started adding fish to my 20 long tank. We have added 3 of the Glofish Danios (I know there are lots of opinions on them, but my daughter picked them out and she loves the bright colors and she's 6) last week. I have kept an eye on the water parameters. I have not had any ammonia spikes, but did have a slight reading of nitrites, so did a partial water yesterday. We are going to go ahead and add 3 more danios to round out their school. Eventually we are going to add a bottom feeder, which was going to be the Glofish cory, but after seeing them in the pet store today, they are a bit bigger than I was thinking. I love the panda cory (so cute)! My temp is right around 77 now, could I slowly drop it over a period of time without harming the danios to have it at a temp that will better suit the panda corys?