Butterflies need a 70g, most need even bigger. The four spot needs a 120g. These fish need to swim A LOT, and a 30g isn't even close to meeting that need. I know they're beautiful, and I understand wanting to have one. I want one too, but don't have one because it would be cruel to the fish because I only have a 30g and 55g. Check out liveaquaria.com in the nano SW
fish section and there are colorful options listed there. With a small tank like a 30g, the fish are going to be smaller. But that doesn't mean they're not pretty. Check out that site and you'll see some pretty options.