Algae - the contradiction?

[chessie6]

I'm a bit confused here .. We use a tarp to cover our pool for the winter for the reason that it blocks the light to help prevent algae from growing. So if algae doesn't like darkness, then why does it grow first and the best under the darkest places in my pool such as under the rungs of my ladders?

Thx,
Jan

 

[Beens]

Well, off the top of my head I would say maybe those little dark places are also the ones with less/poor circulation? Just a thought..

 

[Tanner M]

Do you cover your pool before the water temp reaches 60 degrees or lower? Do you uncover it and start chlorinating the water before the water reaches 60 degrees or higher?

 

[chessie6]

To clarify, we close the pool sometime in October so for us that means the water is around 60, and with an opening in April (which is pretty early for CT) we have never opened to algae. But in the summer, there's always a slow growth of algae in the dark places like under the ladder or behind the skimmer plate .. if it were to grow I would think it would pick the spots with more light, but it doesn't. Maybe then it's not the light but where circulation is poor, as you stated Beens.

 

[chem geek]

Different species of algae have different ideal sunlight amounts for growth, just like plants. Green and black algae tend to like sunlight, but if there is chlorine in the pool then they are prevented from growing except in areas of poor circulation where the chlorine level can get too low. Yellow/mustard algae prefers shade and is also more chlorine resistant.