Goldfish chasing another to death?

Question

I've had two comet goldfish for nearly six months and everything's been fine until just a day ago. One of the fish, Pepper, has been chasing the other, Jack, around the tank. Jack's been lying on the gravel ground for these past two days, either sideways, lying on one of the plastic plants or stuck on the filter uptake grill. Jack has some scales missing. Jack also will pop up time to time, swim a little, then sink back down. Even as I type this question, Jack's lying sideways in the back corner.

I've done a water change to no avail.

Jack also hasn't eaten (Pepper has.)

Pepper (the chaser) doesn't have any white speckles on him..

What's going on here? D:

Answer 1

probably mating time lol

sounds like jack doesnt want that so i would separate the tank with a plexi glass or plastic hard peice with holes in it (that are like really small) and place it in the middle so the are separated so both can rest and eat.

i wouldnt put them back together for a while until pepper settles down!

Answer 2

quarantine jack with rock salt and good aeration until he will be okay.

kOi keeper & goldfish keeper

Answer 3

perhaps is the time when fish have the horny feeling and pepper feels the need to show off his macho-ness lol

Answer 4

He's Physco!