406303A Black Algaetrine Swimming Pool Algaecide & Deposit Control, 32 fl oz, White

After returning home after a long absence, I found that my chlorinator and pump had stopped working and I had a pool full of green and black algae. I started treatment with my usual green/black agaecide which killed the green algae, cleared the water, and got rid of most, but not all of the black algae that had formed on the bottom of the pool. The pool is gunite/pebblecrete which makes it more difficult to remove black algae. After several weeks of brushing and vacuuming, the bottom of the pool was improving but just marginally.I decided to try this algaecide to see if it could totally eliminate what looked like huge stained areas of the pool bottom. This algaecide is a totally different formula than my previous one, and unlike the other one, does not require super-chorination (shocking) of the pool when using. I used half the bottle in my 11.000 gallon pool in each of 2 applications a couple of weeks apart. It seems like it continues to work for 2-3 weeks after application, as every few days for several weeks I noticed the dark areas getting lighter. The key is being patient and brushing with a stainless steel brush every few days. After 2-1/2 months, the dark areas are almost completely gone and the bottom of my pool is back to the Caribbean Blue it’s supposed to be.