We have a 5+ year old 33 gallon tank that is now down to a single (albiet 14 inch) common pl*co. My kids have been bugging me to add some other, more colorful fish to the upper layers. When we first got the tank, we had a school of giant danios for cycling. They all lasted 5 years and chased after anything that we tried to add. We had some red-eyed Tetras that lasted about 2 years. Cory cats only seemed to last about 6 months or less. Any suggestions on something bright and hardy we could add to the mid and upper layers of the tank? Given the size of the pl*co versus the tank, I was thinking about adding either one or two groups of 5-7 smaller schooling fish. I do not use aquarium salt in the tank at this time (we stopped when we got the cory cats and never restarted). Thoughts or suggestions?