Sorry i am never detailed enough on these things. (you can tell im new). Im not new to bettas, im new to biorbs. They seemed good but now ive heard you lot, they sound bad. I was worried about him not having enough surface area to take breaths off of, not worried about him having enough water. I have 3 females in my 30 gallon community 1 bright red, 1 dark blue and 1 pinky white. I have been to the pet shop today and i saw a 12 gallon rectangle tank for about the same price as the biorb, with everything you need for a new tropical set up apart from substrate. The Biorb 30 was £45 and the 12 gallon is £49. He can have it all to himself not having to compete for food, and able to explore all the rockwork caves. It can be his own mini mansion.
thanks
AQUAKING