Perky, that is fantastic. I think you'll be alot happier with this set up especially since you are keeping that nice 2' width. I'm not sure about actual glass thickness measurements but thicker usually equals stronger and when you're talking about that much weight and $$, I'd say thicker is better. You can easily do a marine betta. Panther groupers get 27'' long so that would be a stretch once he's full grown because he wouldn't have enough room to turn around but, yesterday I saw a tiny one here in Tampa at Coral Reef Aquariums that was only about 1-2" from head to tail. They do grow fast though. With the larger size tank, you have a wide selection of Tangs, Triggers, Lions, Wrasses, Puffers, Angels and Grouper. Research your selections carefully from several sources. I found out that the Clown Trigger I want so bad will get too big for my tank in pretty short order plus is likely to kill other tankmates even in a larger set-up. Of course there are tanks that defy all odds. We have a very peaceful 180G at work (which is the tank that got me hooked on this hobby) that contains a Regal Tang, Purple Tang, Yellow Tang, Naso Tang, Niger Trigger, SFE, Large Volitans Lion, Maroon Clown, Onespot Foxface, and a Bamboo Shark (I think not exactly sure of species). They all get along fine, even the yellow and purple tang are buddies. The owner told me everybody was added at once when they were pretty small.