Holy crap...I cannot believe that I actually know the answer to one of the "What is it?" questions.
I actually feel pretty smart right now, even though this is about to be the first thing that I have actually ever successfully identified on here.
Dude...those are creek chubs. They are in the river I live on in Michigan. They are very common and they can survive in Aquariums if given adequate space. I used to catch some with horns on their heads just like that. I've caught ones that are 3 inches long all the way up to 12" inches long. I used to fish a lot in the river from age 10-15. Even though I am 28 now, I still remember catching them, many of them having horns on their head. Their is nothing abnormal about them at all. Nothing is wrong with them. Sometimes we would go out and catch them, then use them for pike fishing.
Here is a description of them that I am including that I found on the internet. Pay close attention to the last few lines.
Description
Creek chubs have a thick body and a broad head. Their mouth is large with the back end of the upper jaw extending beyond the front edge of the eye. They also have a small flap-like barbel that is often hidden in the grove between the upper jaw and the rest of the head, slightly in front of the back of the upper jaw. They have a dark spot on the front edge of the dorsal fin where it attaches to their body. They also have a dark stripe that runs the full length of their body. This stripe is darker on young fish and fish caught in clear water, it can be faint or absent on large adults, especially males. Large adult breeding males have a rusty orange red color to their cheeks, lips, and much of the belly and lower fins. They may also show some of this color on their dorsal fin. Breeding males also have a dark bar just behind the gills and have many large tubercles (horn like bumps) on the top of their head.
I feel extremely confident that you can mark this one solved...
Deerhunter24 (Chuck)