How To Get Rid Of Green Algae In Your Pool

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 Your 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 The 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 that 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.

How To Treat 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 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.

How To Calculate Volume Of Water In Any Swimming Pool

In order to figure out the proper doses of chemicals for your pool, you need to determine how many gallons of water it holds. To do that, you need to use a ruler to measure your pool to find out these four different numbers; Length, Width, Average depth and a multiplier that determines gallons.

So here are the formulas to figure out how much water is in your swimming pool:
These formulas hold true for both Inground pools as well as above ground pools.

Rectangular, Square or Free Form Pools

Length x Width x Average Depth x 7.5 = Total gallons

For example: 16′ x 32′ x 4.5′ x 7.5 = 17,280 Gallons

Circular Pools

Diameter x Diameter x Average Depth x 5.9 = Total gallons

For example: 18′ x 18′ x 4′ x 5.9 = 7,646 Gallons

Oval Pools

Length x Width x Average Depth x 5.9 = Total gallons

For example: 15′ x 30′ x 4′ x 5.9 = 10,620 Gallons

How to determine the Average Depth of a Swimming Pool where the bottom slopes

Below is a side-shot of the “typical” inground pool that has a shallow end (see “D”), then a slope that leads into the deep end (see “C”).

How many gallons of water are in my pool?

First measure the depth of “D”, the shallow end (usually anywhere from 3′ to 5′), and then measure the depth of “C”, the deep end (usually anywhere between 6′ and 12′) . Then, add them together and divide by 2. This is the average depth of your pool.

For example, if your shallow end “D” is 3′, and your deep end “C” is 8′, this would be your formula for the Average Depth:

3′ + 8′ = 11′

11′ divided by 2 = 5.5.

Therefore, in this example, your average depth would be 5 1/2 feet.

Kidney and Irregular Shaped Swimming Pools

There are two methods used to calculate the capacity of irregular shapes. First, you can imagine the pool or hot tub as a combination of smaller, regular shapes. Measure these various areas and use the calculations described previously for each square or rectangular area and for each circular area. Add these volumes together to determine the total capacity.

The total of measurement A plus measurement B multiplied by 0.45 multiplied by the length gives you the surface area of the kidney shape. (A + B = 18 feet). The rest of the calculations you are now familiar with. Try this volume calculation:

0.45 x (A+B) x length x average depth x 7.5 = volume (in gallons)

0.45 x 18 ft x 25 ft x 5 ft x 7.5 = 7593.75 gallons.

Rectangular In-Ground Pool Volumes in Gallons

Pool Size
(in feet)
3.5 ft
Avg Depth
4 ft
Avg Depth
4.5 ft
Avg Depth
5 ft
Avg Depth
12×247,6008,6009,70010,800
14×2810,30011,80013,20014,700
15×3011,80013,50015,20016,900
16×3213,40015,40017,30019,200
18×3617,00019,40021,90024,300
19×3819,00021,70024,40027,100
20×4021,00024,00027,00030,000
22×4425,40029,00032,70036,300
25×4529,53133,75037,96842,187
25×5032,80037,50042,20046,900
30×5039,37545,00050,52556,250
All Answers Are In Gallons

Round And Oval Above Ground Pool Volumes In Gallons

Size48in Wall*52in Wall*
12ft Round2,975 3,398
15ft Round4,646 5,310
18ft Round7,646 8,602
21ft Round9,106 10,408
24ft Round11,895 13,594
27ft Round15,054 17,205
30ft Round18,585 21,240
33ft Round22,488 25,700
12x24ft Oval5,948 6,797
15x30ft Oval9,293 10,620
16x32ft Oval10,573 12,084
18x33ft Oval12,267 14,019
Assuming water depth is 6 inches less than wall height.
All Answers Are In Gallons

What Is Parts Per Million (ppm)

One of the most important calculation you will use is parts per million (ppm). The amount of solids and liquids in the water is measured in parts per million, as in three parts of chlorine in every one million parts of water, or 3 ppm.

To help, this list shows common terms and their equivalents:

Square foot (sq. ft.) = 12 inch wide x 12 inch long

Cubic foot (cu. ft.) = 12 inch wide x 12 inch long x 12 inch high

Cubic yard (cu. yd.) = 36 inch wide x 36 inch long x 36 inch high

One cubic foot of water contains 7.48 gallons

One cubic foot of water weighs 62.4 pounds

One gallon of water weighs 8.33 pounds

One part per million (ppm) represents 8.3 pounds of chemical per million gallons of water.

However, one gallon of chlorine, for example, poured into one million gallons of water does not equal 1 ppm. That is because the two liquids are not of equal density. This becomes obvious since a gallon of water weighs 8.3 pounds but a gallon of chlorine weighs 10 pounds (in a 15 percent solution). The chlorine is a denser liquid; there’s more of it than an equal volume of water.

6 Fun-Filled Swimming Pool Games To Play

Swimming Pool games are always fun and exciting. We must be aware of safety especially when children are participating in these games. These pool games should only be played by those who are able to swim by themselves.

Swimming Pool Safety Rules When Playing Pool Games

  • Children must always be supervised by an adult that can swim.
  • Always put safety first.
  • Always remember water can be dangerous.
  • Children must obey your swimming pool rules.

Swimming Pool Races

With swimming pool races you can use the length or width of the pool. This depends on the strength and how well the children can swim.

The children can either start the race by diving into the water or they can start the race in the water against the swimming pool wall.

Make the race no more than 2 lengths of the pool at a time.

Marco Polo Swimming Pool Game

This is a swimming pool game everybody loves to play. There must be at least 2 children to play this game. One child will be Marco. The child that is Marco must keep their eyes closed during the game.

Marco will shout out the word “Marco” then the other children will shout out “Polo”. Now Marco must find touch and tag any Polo. Once another child is tagged then they become the new Marco.

A Polo is allowed to sneak out of the water and re-enter at the opposite end of the swimming pool. If the Marco suspects this they must shout out “fish out of the water”.

If a Polo is in fact out of the water then that polo becomes the new Marco.

Simon Says Swimming Pool Game

One child plays Simon and gives instructions to the other children for what they must do. Example:

  • Simon sais jump in the water.
  • Simon sais swim.
  • Simon sais go underwater.

If the child who plays Simon gives instruction but does not say Simon Says in the beginning, then the player who follows the instruction is out.

Also if a player does not do a task that Simon instructs them to do is out. The last player standing wins the game and then becomes Simon.

Underwater Race

Children start in the pool at the shallow end against the swimming pool wall. 2 or 3 can race at once. The aim of the race is to see who can swim the longest underwater until they resurface.

The last child that resurfaces is the winner. I suggest only older children play this game as it is too dangerous for younger inexperienced swimmers.

Sharks and Minnows Swimming Pool Game

You need quite a few children to play this game. One child will be nominated as the Shark who will stay at one end of the swimming pool while the other children will be all Minnows at the opposite end of the swimming pool.

The Minnows must try to get past the Shark to his side without being tagged. Whoever gets tagged now also becomes a shark. The game will continue until there is one Minnow left who will be the winner.

The last Minnow now becomes the Shark, and the game starts again.

Treasure Hunt Diving Swimming Pool Game

Weighted swimming pool toys or a 2 liter plastic coke bottle filled with water and the label removed is perfect for this game. When the plastic coke bottle is underwater it is difficult to see.

That’s why it’s perfect for this game.

The children can be either in or out of the swimming pool but they must be facing away from the water with there eyes closed. An adult must throw the bottle or toys in and count to 10.

Only then are the children allowed to find the bottle or toys. The toys can have points allocated to them so the child who collected the most toys wins.