I dont think one is necessary... JMO, but 9/10 tanks under 10g are either bettas or shrimp of some sort... granted there are exceptions. I just dont see how there is a big enough need for a sub-forum that can easily be addressed in either the general, getting started, aquascaping, or breeding sub-forum.
Sub-forums seem to clutter up things more than they help in alot of situations. Going from forum to forum to read the various posts is a hassle IMO
, and then from the management side, trying to keep things in order and in the correct forum would add more work for the mods. Again, thats all just my opinion