can you have algae with no CC and FC available?

[carlos31]

I have some green spots on the lights and drain covers which scrub off. Looks like algae but I have no CC. FC is available. Is it possible to have algae with no CC?

FC 3.0
CC 0.0
pH 7.4
TA 60
CYA 30
CH 960

PH rise is a constant problem but I do have a large water feature that aerates.

 

[svenpup]

Yes. You should do an overnight chloine loss test (you have to turn off the liquidator to do this). If you lose more than 1ppm of FC overnight than you should shock.

 

[chem geek]

If there are areas of poor circulation then algae can form there, but the places you describe shouldn't have poor circulation -- especially not the drain cover assuming the drain is working (are you sure it's working?). There could have been some biofilms formed there at some point that take higher chlorine levels to get rid of so shocking and brushing are the right prescription at this point and then see if it comes back again after you get < 1 ppm FC overnight loss and let the FC drop back down to normal levels.

You might also check behind the light in the light niche for algae and check under any removable ladders as well.

 

[carlos31]

I will definitely shock - I have only done it once and that was over a year ago. I have four lights and four drain covers so removing them all would be a chore.