Discus on a rampage – HELP!!!

[falcon]

My brown, wild discus is going out of control. Yesterday, for no apparent reason, while we were watching TV, the discus just took off at 150mph(I’m not kidding here) and started running in circles, hitting the glass and everything in his path. He was running with such a speed and power. My concern is that he might hurt himself from banging on the glass and could hurt some other fish in the process. He’s in a 120g, planted community tank. He’s probably around 5” or more. Yesterday was a third time that he had done that and it’s all within a 1-month time span. The other times maybe weren’t as harsh. Prior to the incident, he seemed a bit isolated from the other discus, staying on the other side of the tank in the cover of the plants and would just come for a feeding. I have varying sizes of discus there, from 1 ½” to 5”. ANY IDEAS???
                           Falcon

[DarkDiscus]

There are a large number of reasons that could make your discus freak out like that.

Since the other fish don't seem to be acting that way, I'm going to assume that it's not a bacterial problem in the water which can make the fish very jumpy.

Examples I've seen:

1.) Fish with flukes can suffer sudden irritation and freak out.

2.) A shadow passing in front of the tank can cause a fish to freak out.

3.) Similarly, when my wife suddenly turned on an overhead light in the room my wilds tried to bash themselves silly.

4.) I saw one of my fish nip another and send it flying.

And there are probably a half dozen more I'm not thinking of...

John