Planted Tank Enthusiast
Join Date: Jan 2013
Location: Baton Rouge, LA
Agree with kman.
I even have some males in less than a gallon. They get water changes every 5 days, the bowls get thrown in the dishwasher, the fish get rotated to a fresh new bowl, may be up -scaled or down -scaled in size, but seems to add to their enrichment. No one is sick, depressed, or cramped. I have some that seem to prefer smaller, and feel more secure, and others appear to like the roomier accommodations.
My "betta cups" I use as separators for growing aggressive young uns, and those for sale/trade/raok are actually plastic bug observatories from the dollar store. These are roomier than cups, and also dishwasher safe. Comes with a lid and little magnifying glass built in. Long, kidney shape-ideal for young bettas. However, as I "lighten the load", these fish get upgraded to 1/2 gallon jars.
Females get removed from sorority and put in a half gallon jar next to the prospective husband for a couple weeks, to get to know each other and to condition, bred, pampered in her 1/2 gallon jar after for a week in case she gets injured during breeding, then back to the sorority.
The only time I see one depressed is if I'm late for a water change, bi monthly "pea night", or fry-separation-post partum blues.