6 is *perfect* but if they look like they are getting too big, upgrade the tank to a 20g long??? and use a soft sandy substrate!! ive had several people tell me that their kuhlis dont hide at all with the sandier substrates because the know they can hide quickly, thus dont have to hide at all.
also live foods are great too. you live in a decidedly non tropical place, most of the wild caught foods (fruit flies, mosquito larva, daphnia) arent likely (but its not impossible!) have diseases that transfer over to tropical fish. ive been feeding little bugs and mosquito larva to my bettas for a few years now.
OH and decorate away! hopefully the sand will make them feel secure enough to not hide all the time. when shopping for decor for your betta, the softer the better. live or silk plants, make sure that the rocks and driftwood are all soft edged. i use river rocks (fist sized) buried halfway by the substrate, natural drift wood, terracotta pots.... uh.... plastic caves?? handful of different things. oh slate too but i make sure i use pea gravel to take the edge off.
AND I WANT PICTURES!!
Chris- Husband, 04/30/77
Cailyn- Daughter, 07/05/99
Jeffrey- Son, 03/24/06
Alex- Son, 03/25/09
Mister- Black LabX, M, 08/06(?)
The Shadow Stalker- Gray Tux DSH, M, 04/04
The Mighty Hunter- Black Tux DSH, M, 04/04
Baby Girl- Tabby DMH, F, 12/03(?)
Frances- Tortie, DSH, F, 2007(?)