is growth on goldfish normal?

I successfully medicated my goldfish for whatever it was that they had, but
now my water has a pinkish color to it. Any ideas as to why? I used
tetracycline for medication and it initially turned my water color yellow,
but turned back to clear after I ran it through carbon. I've been running
the pinkish water through carbon and doing 25% every other day water change.
I did a 50% water change over the weekend and changed out the carbon, but
the pink color is still there.

Rodney wrote:

I successfully medicated my goldfish for whatever it was that they had, but
now my water has a pinkish color to it. Any ideas as to why? I used
tetracycline for medication and it initially turned my water color yellow,
but turned back to clear after I ran it through carbon. I've been running
the pinkish water through carbon and doing 25% every other day water change.
I did a 50% water change over the weekend and changed out the carbon, but
the pink color is still there.

Did you change all the carbons? If so, you may have thrown your tank
back into cycle