We have been fighting black algae for 3 weeks. After I found this site I stopped listening to the pool store guys which helped a lot. Before then we had a CYA level of 250 which they said was OK. We partially drained our plaster pool and refilled. Next we did several days of shocking in the 35 - 40 ppm range until stopped losing FC overnight and then maintained FC at that level for another 3 days. I was using the DPD extreme FC test to determine FC.
We still have black spots but none seem to have the slimy top coat any more plus we are continuing to use SS brush to brush daily.
I finally was able to afford the full test kit and I have some new numbers and would like input on whether I need to adjust anything at this time.
FC 21.5 (1 ppm drop last night) - planning to maintain FC at 12 based on CYA of 100
pH ?? reads 7.5 but FC levels are high so not accurate right?
TA 110 - is this accurate at high FC levels? Turns blueish color instead of red
CH 250 - had to add reactant before doing test to get the right color and no little specks in the
water - does this mean I should be testing for other metals?
CYA 100 - pool store told me it was 50 three times. Should I do another partial drain or is this OK?
15,000 IG, White plaster, Cart filter, Jet Vac sweep