Today I got home from class to find two of my peppered corys had been spawning. They've been doing it ALL DAY, I got home at 2 and they're still going at it and its 8 here. The female has preferentially been laying her eggs in one corner, on the glass wall perpendicular to the heater and filter. There are other eggs scattered everywhere but that's where most of them are.
I noticed the betta was hovering around them but since I usually just let the fish eat the eggs anyway (I'm in my senior year as a microbio major so I have NO time to be dealing with breeding fish) I wasn't too worried about it. A little bit ago I went to watch the corys mate and lay the eggs, and I noticed the betta was still in the corner, but all of the eggs (in fact, a lot more eggs) were still there. He alternates between staring at them and resting the side of his body against them, and he chases off the rasboras if they get too close, but he lets the corys swim in the corner all they want. I swear he's protecting them!
Needless to say I've since been watching him more than the corys mating because he's acting so funny! Is this common?? It seems crazy to me that a fish could display altruism for fish of another species!