Algae growth at END of cycle?

Yes.You are most likely seeing diatoms not algae.Is it brown??

 

yes, i will be able to use the carbon again after it dries?

yep, it's brown.

 

It's still cycling if you're reading ammonia and just starting to see nitrate. Wait for the ammonia and nitirte to bottom out while you continue to ghost feed. That means the bacteria have built up to sufficent numbers. When you're left with nitrate only, do your water chnages to reduce that number and add fish.

 

how long have you been running it? I probably would use new when you start it up again.

 

only running like 6 days.

 

i was kinda thinking that if i used it after it dried out, that whatever has built up in there, might cause an ammonia spike after it was added back in.

 

I'm not sure about that but I'd err on the side of caution and not reuse it.