I have heard about testing a Bettas temperament to see if they are suitable community fish and I was surprised by the outcome. I had 2 low ranking male guppies(short tailed) in my tank eating the last few detritus worms and added my new betta out of curiosity really to see if he is one of the rare placid ones. He flared for less than 5 seconds and then completely ignored them. The guppies than starting biting his fins and chasing him so I removed them immediately. I was under the impression that betta are the more aggressive fish.