Swimming Pool Tips

Swimming Pool Information

Green water or floating green algae in a swimming pool is a common problem. Several chemicals can be used for treatment. By regular swimming pool maintenance, you can prevent green algae from returning.

How To Use Chlorine To Kill Green Algae In Swimming Pool Water

If your swimming pool water contains clumps of visible green algae, then there isn’t enough chlorine in the swimming pool. “Shocking” the swimming pool with chlorine is the most effective way to kill existing green algae and bring your swimming pool back to life.

Usually, this works within a time period of 1–3 days, but if the swimming pool conditions are poor, it could take up to a week.

How To Remove Green Algae From Swimming Pool Walls


Brush the swimming pool walls and floor. Remove as many green algae as possible. This will reduce the time needed to kill and clear the green algae.

Pay particular attention to the swimming pool steps, ladders, and other areas where algae tend to form.

Make sure that the brush matches your swimming pool. Steel brushes work well for concrete swimming pools, while for vinyl and fiberglass swimming pools nylon brushes are preferable.

Test The pH Level Of The Water


Balance the pH by adding either an acid or a base to bring the level to just around 7.8 before treating the pool. This is at the high end of the range that you would normally have in your pool, but when you treat it for algae, it is necessary as this increases the efficiency of your chlorine and therefore reduces the growth of green algae.

Here’s how to balance the pH level: Turn on your swimming pool pump to circulate the chemicals throughout the pool. Correct the pH level either by increasing the sodium carbonate pH or by lowering it with sodium bisulfate.

It’s more accurate to use test kits that have tablets or droppers than paper test strips. If the pH levels return to normal but total alkalinity exceeds 120 ppm, check the instructions on the pH reducer label (sodium bisulfate) to reduce the total alkalinity to between 80 and 120 ppm.

Choose a suitable chlorine Shock product. Do not use the chlorine that is used for regular swimming pool treatment. Ideally, liquid chlorine for swimming pools should be used. Sodium hypochlorite, calcium hypochlorite, or lithium hypochlorite should be included in the product.

If you have hard water, avoid calcium hypochlorite.

Avoid granular or tablet chlorine products which contain large quantities of stabilizers that should not be added to the pool. Check the product for instructions on how much to use.

Use twice the recommended amount to fight green algae for a regular shock. Use triple the amount if the water is green with thick suspended algae, or even quadruple if the steps are not visible. Add the shock directly to the swimming pool edge with the swimming pool pump running.


Because UV rays break down chlorine in sunlight, add at night as this is when the chlorine is most effective.
Before switching the pool pump on, make sure that the weir basket and pump filter are clear of all debris. If not this will lengthen the filtering process of the green algae.

Check the swimming pool after the pool pump has run for 12–24 hours.

Dead algae turn’s white or gray, either the algae are suspended in the water or it settles at the bottom of the swimming pool. Remember to vacuum the dead algae from the swimming pool floor.

When vacuuming, make sure that the multivalve is on backwash so it does not block the filter. It is advisable to reclean the weir and pump filter after 24 hours as green algae will now be trapped in these parts.

Whether the green algae is dead or not, test the swimming pool water for chlorine and pH levels.

If the level of chlorine is higher (2–5 ppm) but the green algae is still there, keep these levels constant for the next few days. If the chlorine levels have risen but are still below 2ppm, then the next evening “Shock” for a second time.

If the chlorine levels have not changed significantly, your swimming pool is likely to have too much cyanuric acid (over 50 ppm). This comes from using granulated or tablet chlorine, and your chlorine condition can be “locked”.

The only way to fight this is to repeatedly “Shock” or partially drain the swimming pool.


The chlorine strength can also be used up if leaves or other unwanted dirt is in the swimming pool as well as if the pool has not been used for a long time. So make sure that the unwanted dirt is removed. It may take a full week and several “Shock” treatments for the swimming pool to come right if this is the case.


The chlorine should kill the green algae over the next few days. Test the water daily to confirm you have the correct amount of chlorine and pH. A well-maintained swimming pool has these values: free chlorine: 2-4 ppm, pH: 7.2–7.6, alkalinity: 80–120 ppm and calcium hardness: 200–400 ppm, respectively.

Small differences are common, so there should be no problem with a slight deviation.

If you still have trouble with the green algae, add coagulant or flocculant so that it clumps the algae together. Once there’s no green color left in the pool, vacuum up (set multivalve to backwash) all the dead algae until the water is clear.

You could let the filter handle it, but make sure the filter is clean first. If you do not thoroughly clean the filter, the filter can get blocked by the dead algae.

Check for the proper functioning of the swimming pools water jets.

They should point at an angle in the water so that the water moves in a spiral pattern around the swimming pool to get the most effective circulation for filtration.


Adding flocculant or coagulant is the fastest way to make your swimming pool water look good, but it’s not safe to swim in this water. Follow this with a treatment of chlorine “Shock” to sanitize the pool and do not swim in the pool until the levels of chlorine and pH return to normal.

Treating Swimming Pool Water With Algaecide

Algaecide will surely kill your green algae, but it may not be worth the side effects and expenses. Some algaecide products, especially if you have black algae as well, are not powerful enough to treat an existing problem.

Ask a pool store for help, or find a 30 percent + active ingredient product.


Quaternary ammonia algaecides (“poly quats”) are inexpensive but foam your water. This is annoying to many people. Algaecides based on copper are more effective but costly. They also stain the walls of your pool.

How To Remove Phosphates From Swimming Pool Water

In water, algae feed’s on several nutrients, particularly Phosphates. Phosphate test kits are available to test swimming pool water for these chemicals.

Use a commercial phosphate remover from a pool store if they are in the water. When adding Phosphate remover to swimming pool water, let the pool pump run and the water must circulate through the filter for 24 hours.

About 300 ppm is an executable level unless you have recurring problems with green algae. Then this level should be lowered.

Clear Swimming Pool Water.

Keeping Your Swimming Pool Water Clear Is Important

If you maintain your pool chemistry levels, algae should not grow. Test the swimming pool for free chlorine, pH, alkaline and cyanuric acid levels on a regular basis.

The quicker a problem is detected, the easier it will be to deal with. During the swimming season test at least twice a week.


A preventive algaecide can be added to a swimming pool when conditions are normal. Algaecides are best used in small, weekly doses. This will kill populations of algae before they grow. Too much algaecide can cause foaming or staining of your pool walls.