How to Remove Black Algae From Your Pool

Things You’ll Need

• Steel Brush (10" Algae Brush)
• 3-inch Chlorine Tablets (10 lb. Bucket)
• Di-Chlor Shock (12 x 1 lb. Bags)
• Algaecide Prevent 60 Low Foam (1 qt. Bottle)
• Aqua Chek 7-Way Select Test Strips
• Granular Chlorine (2 lb. Jar)

Step 1

ASSEMBLY TOOLS AND CHEMICALS - Buy the required tools and chemicals ahead of time to have them on hand for this procedure. If you have a concrete or gunite pool, you will need to buy a stiff brush like one with stainless steel bristles. The chemicals that you will need to buy are shock treatments and an algaecide.

Step 2

CLEAN FILTER - If black algae are in your pool, it's also in your filter. If you have a sand or DE filter, backwash and rinse your filter a couple of times. If you have a cartridge filter, pull out the cartridge and rinse it off thoroughly.

Step 3

BRUSH POOL - Next you need to brush off the black spots vigorously with as stiff a brush as you can use. If you have a concrete or gunite pool, use a stainless steel bristle brush. If you are one of the few that have black algae in a pool with a smooth surface, use the softer nylon bristle brush. Black algae have a protective cover over the algae roots that penetrate the porous surface of the pool. This barrier has to be removed so that the chemicals can get to all of the algae. Brush the algae spots three to four times a day for the duration of the treatment. Pay special attention to the pool's corners and around fixtures like the pool ladder.

Step 4

WEAR GLOVES AND EYEWEAR - Before you start handling the chemicals used here to treat black algae, put on a pair of heavy vinyl gloves and protective eyewear.

Step 5

SCRUB WITH TABLETS - Break a chlorine tablet in half and scrub the edge of the tablet over the black algae spots. For the areas you cannot reach, buy a tablet holder online that attaches to the pole of your brush.

Step 6

SHOCK POOL - Shock your pool with Sodium Dichlor using three times the normal dosage. So, instead of one pound per 10 000 gallons of water, use three pounds per 10 000 gallons.

Step 7

ADD GRANULAR CHLORINE - If you have a pool with a lightly colored surface, sprinkle Granular Chlorine over all the areas where it may settle on or near the black algae. Do not use Granular Chlorine in pools with dark surfaces as it may bleach the surface.

Step 8

ADD ALGAECIDE - Add one 32 oz. bottle of poly 60 algaecide per  15 000 gallons of pool water.

Step 9

RUN PUMP - If you have a pool with a light finish, leave the pump off for 24 hours to let the treatment set in. Then, after those 24 hours, run the pump an additional 24 hours the next day. For a pool with a darker finish, run the pump for 24 hours after adding the chemicals to prevent bleaching. During this 24-hour/48-hour period, continue to brush three to four times a day where the black algae spots were.

Step 10

CLEAN FILTER - Clean your filter again to rinse out any black algae residue.

Step 11

BRUSH POOL - Continue to brush where the black spots were for two to three days while the chlorine level is still high from shocking.

Step 12

RE-SHOCK POOL - If there is any indication of the black algae reappearing after three days, shock your pool again with a normal dosage - one pound per 10 000 gallons of water.Continue to brush where the spots were for two to three more days. Don't skip brushing. It is a key part of the treatment.

Step 13

MAINTAIN POOL CHEMISTRY - Once you have had black algae, it has a tendency to reoccur. It is important that you maintain your pool's chemistry and that you brush down the pool walls and floor once to twice a week. Note: Due to the heavy chlorine treatment, the chlorine level may remain high for up to two weeks.