someotherguy wrote:
What causes algae growth? Just lack Of chlorine? can algae grow with 2fc? Everything is great now i just want to keep it that way
Algae spores blow in the wind and when they get into pool water (or fall in from algae growing on surfaces above the pool water) they can grow if there are nutrients in the water and there is not enough chlorine to kill them. It is a competing race between the rate of algae growth and the rate that algae is killed.
The algae growth rate is faster at warmer temperatures and usually with more sunlight (except for yellow/mustard algae that prefers shade) and the rate is faster at higher nutrient levels including phosphates and nitrates. However, the growth rate is ultimately limited by temperature and sunlight regardless of the nutrient level in the pool.
The rate of chlorine killing algae depends on the active chlorine (hypochlorous acid) level and that is roughly proportional to the FC/CYA ratio. So the answer to your question if algae can grow with 2 ppm FC, the answer is yes if the CYA level is above roughly 25-30 ppm in a manually dosed chlorine pool. Basically, most algae will be killed faster than it can grow if the FC level is maintained relative to the CYA level as indicated in the
Chlorine / CYA Chart.