The HTH Ultimate Algae Guard is the one that is added every 90 days, it is a copper based algaecide.

Does algaecide contain copper?

Pool chemicals known as algaecides can treat or prevent algae growth. A popular type of swimming pool algaecide is based on copper compounds. Copper-based algaecides are effective and relatively inexpensive, but should be used with caution to avoid problems.

What algaecide does not contain copper?

Locey Clear 60 by Haviland is a 60%, poly-based algaecide that contains no copper. Clear 60 algaecide works for pools with salt chlorine generators, or for families that have a lot of people with light-colored hair (copper is what turns hair green, not chlorine!).