Wondering what you guys think of keeping only male guppies? I didn't find much information on it when researching stocking for our 20gL. I decided to try it and brought home five male guppies. There is also a group of cardinal tetras in the tank. Everyone gets along well except for this one guppy! He's a pretty green cobra that my son picked out and he seems to have established most of the open area in the tank as his territory. He chases all the other guppies away and the tetras give him space because he is so spastic, although I have not seen him go after them. The other 4 guppies seem friendly with each other and are trusted by the tetras too. The 4 get chased by this guy every time they cross through the open area of the tank. So, do you think it's just his personality, or is it possible that green cobras in general are more aggressive? Or, could it be, that in an all male group, one guppy will establish himself as a leader?