Problem Summary
Pool wall surfaces feel slick or slimy to the touch, even when the water still looks clear.
A slippery, slimy feel on pool walls is a biological growth issue — usually an early-stage algae or biofilm — even before any color change is visible in the water.
Possible Causes
Early-stage algae growth not yet visible in the open water
Algae typically colonizes surfaces before it's dense enough to visibly tint the water.
Low-flow zones along walls and corners
Areas the circulation doesn't reach effectively let biofilm establish even with acceptable bulk-water chemistry.
Diagnostic Steps
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Test free chlorine and pH.
Low free chlorine or high pH both reduce disinfection effectiveness against surface growth.
Solutions
Brush all surfaces, then shock the pool
Addresses cause: Early-stage algae / biofilm
Brushing disturbs the biofilm so chlorine can reach it; treat as an early algae case using the Chlorine Calculator.
When to Contact a Specialist
If slipperiness returns quickly in the same spots after cleaning, those may be genuine low-circulation dead zones that need a mechanical/hydraulic review rather than repeated manual cleaning.