Since you have a breeding pair on cons, it would be much better to let them have the 30 gallon to themselves and keep your severums in your new tank. Three is not really a very good number for cichlids, its often the case that two will pair up and beat on the third

I'd keep a close eye on them in case that does happen, if so, you'll need to remove the "third wheel" either to its own tank or back to the petshop.
If you're after info on severums, here's a profile on them
http://www.worldcichlids.com/fishprofiles/severums.html