I think you're right about mounting them separated. I believe on Emster's build thread they were mounted apart. I left small gaps between mine because I wanted them to grow in faster.

The nice thing about the travertine is that it's really nice and heavy. I cut out a bunch of discs for future frags..

The other thing I found, is that my red ones grow much faster than my green ones. Time shall tell what happens in the next couple months :biggrin: