reddish/brownish/maroonish algae???

Hi Again! I've been researching the cyanobacteria and also the LFS gave me a powder called Chemi-Clean for cyano bacteria. I've used 2 doses (48 hrs. in between as suggested.) It says one level scoop per 10 gallons. Although, I have about 18 gallons, I kept w/ one scoop due to the LR, etc... and would rather underdose a little...

There is an improvement but still some there. Also, I'd rather get to the root of the problem so it won't keep coming back... Many of the things i read mentioned high nitrate and phosphate in the tap water as a problem.

I thought about an RO unit, but tested my tap water and the nitrate was 0 and phosphate 0 or MAYBE 0.25... SO, I don't have to really get an RO unit, right? I add 1-2 quarts of tap water to my tankk (dechlorinated) every day due to evaporation, so if my tap was bad I thought that could have caused the cyanobacteria. How is my water flow based on info I gave above??? I will do more water changes.

The levels in the tank are all good. 0 ammonia, 0 nitrite, practically 0 nitrate, ph is 8.4...

They didn't have an alkalinity test, so that's one thing I havent done yet... Any thoughts?
 
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