Pool Algae Types in Avondale, AZ

Green Algae — Common and Fixable

This is what people mean when they say their pool went green. It floats free in the water, which is why it clouds everything and why it responds well to treatment: shock the water, run filtration hard, brush the surfaces, and it comes out over a few days.

It appears when chlorine drops below the line for a few days in warm water, which in an Avondale summer takes remarkably little. It is the most common algae we treat and the least concerning.

Mustard Algae — Sneaky and Persistent

Yellow-brown, usually on shaded walls and in corners, and often mistaken for sand or dirt because it brushes away easily and then reappears in the same place. That is the giveaway: real dirt does not come back.

It resists normal chlorine levels better than green algae and it survives on surfaces rather than in the water column. Anything that touched the pool — floats, brushes, swimwear — can reintroduce it, which is why partial treatments fail.

• Yellow or brownish, on walls rather than in the water
• Brushes off easily and returns to the same spot
• Prefers shaded areas and steps
• Needs a higher shock level than green algae
• Requires cleaning equipment and floats too

Black Algae — The Hard One

Dark spots with a protective outer layer, rooted into plaster rather than sitting on it. It appears most often in older, rougher surfaces where it can get a grip — which is exactly the plaster you find on Avondale's older pools.

You cannot chlorine your way through the protective layer, so treatment means physically breaking the heads open with a stiff brush and treating aggressively, repeatedly. On a badly established case, an acid wash on a drained pool is sometimes the realistic answer.

Why It Keeps Coming Back

Recurrence almost always means something structural. A rough or pitted plaster surface gives algae somewhere to hold. Poor circulation leaves dead spots that never get sanitised. And chlorine that dips even briefly each week gives it the window it needs — which is the honest argument for consistent weekly service.