Originally Posted by mr_X
I wouldn't add any chemicals to the tank. Water changes/upping nutrient export, and cutting back on feeding would be what I would suggest. I would not add another fish to the bio load to correct this problem either.
I agree with Mr. X as far as adding another fish. That is not the answer
If you have cyano
there's most likely one or two underlying problems
1) you either have too many fish in your tank or
2) your not doing enough water changes
Cleaning your tank once a week and doing a water change SHOULD be sufficient. And when I say clean I mean CLEAN. Try to remove all of the algae from the rocks (a tooth brush works great. It's tedious but it works) and siphon all the algae off the sand.
However I do not agree with mr. X when he says not to use chemicals. I use Algaefix and it works wonders if you use it properly. Only AFTER you have removed all the cyano
you possibly can from the tank and done a water change dose your tank. I believe it's 1ml for every 10 gallons or 5ml for every 50 gallons.
However it will NOT work if you have activated carbon in your tank or filter so if you use chemical treatment you will have to discontinue using activated carbon until you have completed the treatment.
After that your supposed to dose Algaefix every 2-3 days until the cyano
Once you have gotten rid of the Cyanobacteria I can not stress enough how important it is to keep doing water changes once a week or it will come back, especially in a fish only tank.
There are a million other things that can contribute to cyano
but I found these as the main causes as it is fueled by nitrates and phosphates, and without some sort of macro-algae to export nutrients I'm afraid your best option is high maintenance.
Good luck hope this helps