So this has been a long time trick of betta breeder's. You no the one's that keep 100's and 100's of bettas. Ive even seen some people drill hole's and make a drip system with them. But me i just do 100% water change's. I do have a drip system but not made out of beanie baby box's. Anyway they do not cost that much and they give for plenty of room. So it can be a home for ever or just untill the betta sell's but either way he will be happy.
Here i will post some picture's i found on the net im trying to get my camera working. Think my girl broke it when she took it to the beach. dam!!

Beanie baby box's side by side.

Diagram of beanie baby box

More bettas in beanie baby box