Well, I moved both of the severums today. I have been checking on them tons, and watching. So far, they have been very good with not beating eachother up. Had/having water temp issues, just trying to get that fixed...hmm, will be continuing to watch them closely but there is a decoration and a couple plants in the 20 with them, so they have room...and spaces to hide. My bf said they are closer to 4 inches for the larger and 3 or 3.5 for the smaller.. see... I know I have poor "estimating the size of fish" skills.... lol