I would guess that it is a fantail darter but thats without trying to key it out or anything. That same site the sculpin article came from has darter articles as well, check out the article section on nativefish.com
I would suggest you get a copy of the Peterson Field Guide for NA freshwater fish. And also familiarize yourself with the protected species in PA. If you are going to continue collecting fish, do yourself a favor and do both.
Hey had the exact same darter that I have been looking ID for because of the fact that most of the darter profiles that fit mostly- had the blue on top of red on the fin, I could not find pictures of darters with the exact same as this one the red on the top of blue.
Drove me nuts and am glad I'm not the only one thats looking for species ID- it was in the minnow bucket with all other fathead minnows. It was put into a 120 coldwater tank few months back and its no more as have not see it since.
my suggestion would be go back to the place where you got them and sweep a net in the water to catch any live food that might be there. Introduce that to the tank as well as introduce live brine shrimp and other live stuff they may only go for live stuff not to much pellets to be found in the wild. While you are at point of origin take temp readings and water tests to see if you can replicate in your home tank