I didn't even try housing my boys together. I divided my tanks and everyone lives in their own little section, but it took a little trial and error because of the placement of the filter. Tuffy ended up getting into Trigg's section. Thankfully I saw it before they could get to each other.
I hope you're able to keep both of your guys. Are the names a reference to Chrono Trigger? I love that game (and Magus was my favorite character)!