Help Me!

[littlethibeau14]

OK. I know this is not a tropicl fish but I didnt know where else to go for help. I got this comet goldfish from petsmart for 25 cents and ever since i bought him he did this weird thing with his color. He started off gold but now hes slowly turning black. I looked everywhere for a disease remedy but i couldnt find the right one. Now im getting worried that its something serious because he not as active as he used to be. Hes sitting on the bottom of the tank. I have a bubble wall in there to pump oxygen but I don't know what else to do. Anybody here who is familiar with this. I will try to get some pics on here as soon as I can.

 

[*Fishkies*]

What size tank is he in and what type of food do you feed him?
Does he have any tankmates? How long have you had this goldfish?

 

[WILDER]

Need size of tank and water stats like the above member has asked for.
Any signs of flicking and rubbing.
Is it possible to get a pic up to take a look at.