We have an in-ground 25,000 gallon gunite pool that uses a SWG. I have been battling mustard algae for the last month. I have used a number of different algaecides which hardly worked. Finally got a copper based algaecide which worked and also shocked the pool every few days, sometimes with bleach, usually with dichlor shock.
This week I have been brushing the pool on a daily basis to make sure algae does not return. Two days ago I put in 3 lbs. of dichlor shock. Yesterday I tested my water with two different test kits. FC was above 3. Took two bottles of water to two different pool stores and got different numbers from each, which adds more confusion, but still FC was above 3 in both those tests. Today I tested the water again and FC was below 1.
What the heck is going on? I do not see the algae growing again but have maintained my brushing routine. I am at a loss. I'm almost ready to dump all the water from the pool and refill it. Can anyone help me with this? Am I still battling the algae or is there something else that is using up all that FC? Could it be the algaecides?
I've tested the water coming out of the salt cell and it has FC so I know that it is working.
Thanks in advanced for any help.