Update on keeping bettas with Whisker Shrimp.
Both Sparks (my mom's crazy shrimp-killing betta) and Armageddon (my massive 2.5" long in body boy) have whisker shrimp in with them. Armageddon has a breeding pair, and Sparks has only a male. Sparks, of course, goes after his shrimp with a passion, and has managed to cause open wounds on the poor shrimp. Despite my protests, my mom insists on keeping the poor shrimp in the tank with him. However, Trident (my mom's shrimp) is resilient, and is hanging in there. He's about 2" long now, and if he lives long enough, should get about 3" long and be able to properly defend himself, hopefully. He has swiped at Sparks but has caused no damage.
Armageddon is gentler by nature, but he has gone after Madame (the female whisker shrimp) before when fighting over algae wafers (silly fish doesn't know he's a carnivore). Madame, despite being small for her age at only 1.5" long (she puts more effort into developing eggs than growing) has no problem standing her ground and swiping at the betta until he leaves her be. If this fails to work then she hides behind Monsieur, who is already 2.5" long, and he gets Armageddon to back off. Armageddon is a half-moon, and has received no tears in his fins or other injuries. These two also coexist with 3 snails, 2 neon tetras, and 1 5" long pictus catfish with no problems. They actually share a cave with the catfish and they still all get along perfectly.
Feeding wise, they come up to the top during feeding time and grab left over fish flakes and betta pellets, pick algae off of the tank, eat decaying plants, and love algae wafers (as does the catfish). If my filter gets plugged up with decaying plant matter, the shrimp will sit on it and eat the plant matter off until it's all gone, and the filter continues running smoothly.
I shall continue to recommend these shrimp for any betta owner. They should be kept in at least a 3 gallon tank. I kept my first one at 3" in a 3 gallon stocked to the gills, so to speak, with live plants and he thrived.