Green Algae, won't go away !

[riekl]

I have a 40g freshwater taken with Angels, Molly's and 2 pleco's.

I had a HUGE (whole tank green) algae bloom this summer took the water to the local pet store and they said my phosphates and nitrates were off the chart. Great ok so I have spent the past 6 weeks fixing my water chemistry. My Phosphate and Nitrates now read 0 on the dropper test kits, I do 20% water changes twice a week. The fish seem quite happy but this green algae won't go away! I have to scrub the glass on my tank almost daily (well not really scrub the algae just falls right off). I was told once the phosphate and nitrates were gone without food the algae would stop growing but that doesn't seem to be happening. What else can I do to fix this short of nuking the whole tank which I don't want to do?

 

[mambee]

You can add lots of live plants, including floating ones. You can also grow some houseplants, like pothos, with their roots in the water. All of this works to suck up nitrates. I doubt that your nitrates are really 0. Maybe this is the nitrite reading?

 

[Fresh2o]

You did not mention what type of light fixture(s) is on the tank and how many hours of the day it is on. Reducing the amount of light or the number of hours it is on will probably have the biggest impact on the presence of algae. Generally shooting for 6-8 hours per day is a good start.
You did mention that the algae is "falling off". Does it appear slimy or web like or grow in sheets along the glass surface and other surfaces? If so, this might actually be Cyanobacteria or blue green algae (BGA). Frequent water changes and short term direct spot treating with hydrogen peroxide might help control this. Physical removal via siphoning should reduce spreading (be sure to rinse the siphon hose and water change bucket well). A long term effective treatment is erythromycin (EM). API sells EM in most big box stores and LFSs. I've used it in the past with success.