I'd recommend against chemi-clean and go with treating the root cause.
This might solve it for the next couple of weeks but it will eventually return if you don't fix the main issues.
I have had first hand experience with cyano and chemi-clean.
Please focus on getting good test kits and good husbandry, especially on a 20 gallon tank.
Look for test kits on Alk, Calcium, Magnesium, Nitrate and Phosphate.
I believe trochus and cerith snails might nibble on cyano and will also help with algae and diatoms as well.