How to add Borax

[chem geek]

The CYA was 55, and by accident I got the chlorine at that time to 40 ppm but did not hold it there.

What would be the best course of action now? Take chlorine up to 45 ppm and hold it there for how many days?

Well, assuming that what you have is this yellow/mustard algae, and that's a big assumption, with a CYA of 55 I think holding an FC level of 40 ppm should be enough but it will take a few days or possibly a week to get rid of this stuff. It seems that most people who finally decided to use such high levels of chlorine did start to see a reduction in the algae after a couple of days and then full clearing usually within a week. For those that took longer, I am not sure if it's because they didn't have a high enough chlorine level, but suspect that is the case.

It seems that to get rid of the yellow/mustard algae that the actual disinfecting chlorine level needs to be at least 1.0 ppm which corresponds to around 2 ppm FC if there were no CYA present. The 55 ppm CYA level requires somewhat less than 40 ppm of FC to achieve this 1.0 ppm disinfecting chlorine level.

Given the reduction you are already seeing due to the Borates, I suspect that after final removal of this algae infestation, if that is what it is, you won't see it come back due to the Borates. At least that is the hope. With several users now using Borates, we'll see if any get the mustard/yellow algae bloom next year. We won't really know for sure until enough users, especially those that typically get the mustard/yellow algae, use 50 ppm Borates.

Richard