I have three gold barbs in my 20 gal tank and yesterday I noticed that the two that I think are males had a red color on their undersides, they are visibly smaller than the other barb and the other barbs stomach did not turn red. Is this a sign of spawning. I assumed they were trying to mate because the two smaller barbs chased the big one all around the tank for a few hours. Today the red is not as bright as yesterday.