the tank the co2 is going in hasn't got a problem with algae. its another tank ;p co2 doesn't cause algae nor does nitrates or phosphates.
fluctuating co2 does. help some algae out (like BBA)
nitrates can worsen the effect of algae if out of balance with the other minerals plants need. same with phosphates
circulation is key.
its stag horn algae im trying to get rid off out of 2 of my tanks (the sig one doesn't have it in..) and its cloudy water in my sig one im trying to get rid of. but it seems to be clearing up on its own. (new tank so i think its just settling down a little)
fish... in the sig tank? none at the moment...
in the tank iv got algae in 2 otos 2 guppies (its 20l, im planning on a betta in the future for it. i know its mean to keep them in there)
in my 120L iv got a female betta. endlers guppie,4 otos, 10 amano shrimp, 1 sunset platy (+3 fry), 10 neons