If you can find a suitable mantis, it would be sweet. Finding them is the tricky part. Anything that grows over 3" or 4" is too big. Here's a list:
http://www.ucmp.berkeley.edu/arthrop...raca/royslist/
I've got a 2.5" G. smithii. I have it in a 6 gallon cube with 1/4" glass. It's smacked the glass several times without any damage. I had it with a three-Stripe Damsel for a few months (in the 6 gallon, then in a 13 gallon tank) and they got along just fine. I just moved the mantis back to the 6 gallon, as I modified it while in the process of downsizing my tanks.
WRT puffers, three Dwarf Puffers would do okay in the 10 gallon, but they're freshwater. One Figure 8 puffer might fit in a 10 gallon, but that's one of the light brackish types.
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