I'm just happy to help out and teach new things Trunkz.
And I know the feeling, I was excited when I got my 10 gallon too and thought I could put whatever I wanted in there! But what I did put in there ended up dying from a very bad case of Columnaris, all 10 fish ended up dying bad deaths :( And it was my fault for not doing better research on it :(
But you are right, some people have extreme
luck when putting fish together, I'm not saying you shouldn't listen to our suggestions.
Generally it's good to listen to others who have tried those combinations before and look at if it did or didn't work out. Like Agent13 said up there, danios are super hyper and need lots of room to swim, even those Glo Danios (who are super expensive anyway
As for putting things back in your 5 gallon, I would definitely not suggest putting a whole school of danios in there lol, or really any other school. So if things don't work out, you could put your four girls back in there and that would be good, and then let the danios and whatever other fish have the 30 gallon all to them selves!
I'm not sure if I showed you this site or not yet, but it's a good calculator for your tank to see how much it could maybe hold: http://aqadvisor.com/
So just put in your tank dimension from the drop down menu and then your filter(s) and then put in the fish you want!
It's great because it tells you how much you need to do a water change every week and how much your tank can hold. Preferably keep the Stocking levels under
100% to give you some wriggle room if anything does go wrong. And then keep your Maximum filtration above
100% to make sure your filter(s) can handle all those fishy's :)