Overcrowded? worried on my 55

I am worried that my 55 gallon tank may be getting a bit crowded. I have four fish in it. A fat sleeper and two brown bullhead around 8 to ten inches long and a four or five inch redbreast sunfish. When the sleeper and one bullhead are on the bottom and the other is wedged into its fake stump it is hard to tell, but at feeding time it looks a little crowded. They have also started to get aggressive at feeding.

What should I do? Is this overcrowded or merely looking that way at feeding? If it is I have no room for a larger tank sadly (if I did I'd get one) and don't have the heart to kill them.

I also wonder why my two brown bullhead look so different, one is greyish with narrow fins, the other is blackish brown with full flowing fins.

If it is I have no room for a larger tank sadly (if I did I'd get one) and don't have the heart to kill them.

Those are not the only options. You can post them on aquabid and send them away for the cost of shipping. You could post an ad on craigslist or at your local fish club. Usually including the phrase "If someone doesn't rescue this thing I'm going to have to kill it" will make people move fast. My color culls always go really quickly on aquabid.