From your picture i don't think it's hair algae. Its just some algae coming with new setups and will be gone after a while. Otto will take care of it. Also. The drop checker is yellow i think. You can tell if there is too much co2 by watching if the fish come to the surface gaping. Best of luck!
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I'll keep trucking then. Perhaps turn the CO2 down a notch, although I did only just put the drop checker in 30 mins before that photo.
The fish are behaving fine. Trying to eat anything that goes in, such as the drop checker in the photo. Not seen them at the surface since setting up. I did use the filter media from my old setup, which I think has boosted the setup time.