Fish (not dish) experts _do not_ recommend 10 gallons for a betta. That's absurd! This well-meaning, but clueless PETA writer needs to get a life. I am against cruelty in all its forms against any species, including _Homo sapiens_, but some of the PETA people would be at the top of my list if I were to suddenly have a change of heart.
As a former fish magazine editor and fish writer of 20-odd years' experience, please let me reassure you that you are doing just fine by your betta, and yes, the building of bubblenests is a sign of good keeping conditions. (I always prefer to say experienced rather than "expert" because there's always something more to learn.) I feel a little sorry for the lone male building his nest over and over again with no chance of female companionship to allow him to complete the reproductive cycle. I know it's silly and anthropomorphic, but there's something about the pleading look in their little eyes as they continue to blow their bubbles that gets me right in the gut. Raising baby bettas is a lot of fun. Would you ever let them get together just once?<G> The sight of the male betta doing all that child-rearing work is just so inspirational. The way he treats the female once he's had his way with her though, can be pure murder, so remove the female the instant spawning is finished. Since they may "do it" while you're not around, the use of floating plants, a somewhat larger container than you are now using, and places for the female to hide until you return to rescue her is a good idea. Okay, that's it, the 10-gallon-tank-advice mystery is solved. Yes, fish experts would recommend a 5- or 10-gallon-tank as ideal to BREED bettas as this would give the female room to escape the male's attentions after spawning. Though she has provided the eggs and shown him a good time, he is hard-wired to see any fish other than himself as a threat to the eggs and later the fry, so he will chase her off after spawning and if she doesn't have enough room to get away from him, she could be killed.
People who send insulting messages such as the one you received are a bit daft and don't have the common sense to realize that if someone were really into abusing animals, they could find much worse things to do than keep a fish in a small bowl. Just count your lucky stars that she doesn't have your home address!
FWIW, I used to get letters regularly from a save-the-animals type in California---elaborately decorated by hand with butterflies and all manner of fanciful creatures---with a return address from an Orange County hospital. These weekly missives made me very glad she was on the "inside," and not out where she could come and fulfill her threats against me for giving advice on how to keep tropical fish in the aquarium rather than out wild and free as God intended. I hope that her venting on me prevented her venting in other, more dangerous ways. It takes all kinds, doesn't it?
Mary Ellen Sweeney