is the copper gone when algae appears?

I treated my tank with copper a few months back to cure some sick fish. The fish were treated for about a month and I started to remove the copper with carbon and water changes. Since the first addition of copper I have done 4 20% water changes on a 65g as well as running carbon. Now algae is starting to reappear. Does that mean the copper is gone? I read that copper will kill algae. I know there are copper test by those aren't 100% so just wondering if anyone has experience with removing copper. Thanks

 

What did you use? Copper Sulfate, Copper Sulphide, or Copper Citrate? While it does have algaecidal properties, it could very well just be at low enough levels to allow algae, yet it would still be high enough to kill snails and other inverts.

 

copper sulfate

 

That's going to leach out of your rock and sand for some time to come yet. I would go buy some Cuprisorb.