POOL/SPA Poolmaster Orthotolidine (OTO) Indicator Solution - 1/2 oz PreviousPoolmaster Indicator Solution - 1 oz NextPoolmaster #2 - Phenol Red Solution Poolmaster Orthotolidine (OTO) Indicator Solution - 1/2 oz Poolmaster Orthotolidine (OTO) Indicator Solution - 1/2 oz $3.25 For maintaining proper pool chemistry! Quantity: Add To Cart Facebook0 Twitter