Algae When Opened The Pool, What Do I Do?

[RGBK]

I had green algae in my pool when opening and had to drain it but obviously couldn't get all of it out, I also need to adjust the chemicals. How do you recommend me getting rid of the algae? Should I do all steps necessary to get rid of the algae before or after I adjust all my chemicals? Thank you!

[chem geek]

1. Get yourself a proper test kit -- the Taylor K-2006 (not the K-2005).
2. Test your Cyanuric Acid (CYA) level and if it is high (especially > 80 ppm) then do a partial drain/refill to lower it.
3. Lower your pool's pH with acid to 7.2
4. Shock your pool with an elevated Free Chlorine (FC) level that is 40% of the CYA level and maintain that level. This high FC is why it is best to reduce the CYA level first since you'll have to do that eventually anyway. Remember that shocking is not a one-time thing. You MAINTAIN the high FC level by adding more chlorine as needed and in the first stages that may be frequently (several times the first day, less frequently after that perhaps twice a day then eventually once a day).
5. Run the filter 24/7 and if the pressure is already elevated, backwash it. If you have a sand filter, then you can add DE to it to improve filtration, though it will get removed with every backwash and need to get re-added. You don't add much -- probably 1-2 cups of DE total added 1/4 cup to 1/2 cup at a time by mixing in a bucket of water and slowly adding to the skimmer. You wait a couple of minutes then check the pressure on the sand filter and when it has risen at least one PSI you stop adding the DE.

6. You stop shocking and let the FC drop when you meet three criteria: 1) the pool is clear with no visible algae, 2) you measure <= 0.5 ppm Combined Chlorine (CC) and 3) you lose <= 1 ppm FC overnight when the sun is not on the pool.

[Alan Samual]

Great Advice by Chem Geek. However, most pool stores will test your water for free, saving you from purchasing your own expensive water testing equipment. I have used Baquacil and their algicide has seemed to work very well, unless you are not using the full line of baquacil, I'd stick with a different algicide.

[waterbear]

Much pool store testing is suspect, to say the least. Owning your own quality test kit (NOT strips) is a wise investment.

Biguanide/peroxide (Baquacil, SoftSwim, Revacil, etc.) does not kill algae like chlorine (or bromine) so an algaecide is necessary with these systems. In a properly chlorinated pool it is not. In an overstabilized chlorine pool it is. The only algaecide that can be used with biguanide are linear quats and they tend to sting the eyes and foam. For a chlorine pool, IF an algaecide is going to be used, polyquat 60 is a much better choice.