It wouldn't be hard to make one.. Well. Not to make
it's another story.
I co-created a now very successful online poetry magazine, originally using wordpress. It was a lot of work, when there wasn't staff for every major job (art, poems, interviews, etc) and two of us were doing everything.. If anyone wanted to make an online magazine, I'd recommend having a good host site with good tech support! (so invaluable), and somebody on staff with the patience to tinker with the coding (which wasn't me xD).
There's also some brilliant print-magazine companies, a bit like lulu.com (but not lulu..) - you pay for the setup, and marketing is up to you, but they print on demand, which means you're not stuck with shipping costs or boxes full of last month's unsold magazines. You can also handle all sales monies and whatnot online.
If anyone has the time and dedication to put in (and plenty of both) and is good at making and keeping deadlines, I highly recommend running a small magazine as an interesting and rewarding experience. I am pretty sure you'd never run out of article material where bettas are concerned! You could run a monthly picture comp, interview Thai fish sellers and betta experts, test run products.. all kind of great things to share! And having an 'ethical-only' policy for ads and review items would help spread word about good betta keeping :) I hope somebody takes the challenge and does it - an online/downloadable betta-focussed zine would be awesome.
I know I'd be in line to subscribe, for sure!