How To Kill Tough Pool Algae Tips and Tricks

Oh No – Green, Yellow and Black Pool Algae!

The three main types of algae you have to kill in a swimming pool is green, yellow-mustard and black algae. The easiest algae to kill is the green algae. The next hardest is the yellow or what we call mustard algae. Black algae is the most difficult to kill because it can embed itself into the pool surface and it forms a hard crust like shell over the top of it. I have seen where black algae can actually grow through a vinyl liner. I know it’s hard to believe, but it can. This can make the job of any homeowner or pool service professional challenging.

It’s time for another swimming season with the warmer temperatures so it’s time to start opening up the pools that have been winterized. The longer you wait to open and the warmer it gets, the better your chances of dealing with algae and the high cost of killing and removing it. If you have been keeping chlorine in your pool all winter it should not be much of a problem but the longer you wait to open the worse the algae can get.

Here are a few tips for identifying and eradicating pool algae.

How To Kill Green Algae

The most common form of algae found in swimming pools is green algae. It is the type of algae that can suspend itself in the pool water making it look like a farm pond. It can also attach itself to the floor and walls of the pool. Green algae can grow and spread quickly if not properly sanitized and is a result of poor pool circulation. Problems with pool water usually starts with the water looking cloudy. This is the time to test your water with a professional test kit or bring a water sample into a pool company to be tested.

pool with green algaeGreen algae spores can be found during sunny and warm water climate and especially when there is a lack of chlorine. It’s very easy to cross contaminate pools with swim suites and toys and games that have been exposed to algae from lakes and rivers then brought into a residential or commercial pool. Pool professionals know how easy it is to transfer algae from one pool to another and know to clean their nets, brushes, hoses and poles before cleaning the next pool.

The best way to kill green algae is to introduce high doses of chlorine shock into the pool which is called shocking the pool. Raising the chlorine level to 8 to 10 parts per million instead of the normal 1 to 3 parts per million that is needed to maintain proper chlorine levels. The process of killing green algae can be accelerated by adding a strong 60% algaecide. Before treating the pool with shock or algaecide it is recommended to vacuum the algae out and then brush the pool. This way you’re only having to treat and kill a smaller amount of algae. Be sure to clean out the filter by either backwashing the system, recharging the (D.E.) filter or cleaning the cartridge filter.

If the pool water is properly balanced and the phosphates levels are at a minimum (less then 200 ppb), it’s rare for algae to form and grow in your pool.

How To Kill Black Algae

Black alage is easily identified because it will appear on the pool plaster as black dots. If your pool is heavily pitted or etched this is a great place for black algae to start growing. The water circulation is not that great in these areas thereby making these places prime real estate for black algae to grow.

Gunite or concrete pools have the most issues with black algae but I personally have seen black algae grow through vinyl liners. In this case it is extremely hard to rid the pool of this type of algae. Usually this liner has to be replaced and the surface will need to be dried out and treated with liquid chlorine.

Black algae can be brought into a pool by dust that is blown in by winds and storms and is more prevalent in dry rural areas where there’s lots of farm animals and agriculture. If .your pool surface is deteriorated, rough and has cracks you have a better chance of getting black algae wanting to to grow in your pool. More common places to see this type of algae is around the light, ladder rails and broken tile.

If black algae is present, you will want to begin treatment immediately because the larger the spots appear the deeper the algae is embedded into the plaster. This makes it a lot harder to kill it off. Because of the hard crust or coating of the black spots, a stainless steel brush is needed to remove the hard surface covering the algae. This coating helps the algae to be more resistant to chemicals that are trying to kill it.

It will take several times brushing to start having an effect on the black algae. It should be a daily routine followed by chemical treatments to rid your pool of this problem. Depending on how bad the black algae has become, you might not be able to get rid of the algae altogether through the remainder of the swim season.

After you have vigorously brushed the algae, it is now time to chemically treat the pool to help rid the pool of this monster problem. It is recommended to use granular trichlor for the flat surfaces along with a copper based algaecide that is for the sides of the pool. It will also help with the algae that has formed on the floors and corners. Try using the trichlor (granular chlorine) first. If you can concentrate the trichlor on the spots will be best. The way to do this is turn off the pool and let it set for an hour or two. Then pour or spread the trichlor onto the spots. If it can sit on the algae spots long enough it will kill of the algae.

For black alge on the walls you will need to use the copper based algaecide for it removal along with daily brushing with the stainless steel brush. Slowly over time the algae will be killed of but not without some elbow grease (brushing). Be aware that if you have metal in the pool water to begin with using the copper algaecide at high dosage can stain the pool walls and floors. The use of a metal control is recommended to be used along with the copper algaecide. The metal control product also helps in softening the crust layer of the black algae allowing for the chemicals to have a better effect on killing it off.

Keep in mind that whatever spots that come off should be removed by vacuuming them to the filter to be cleaned out. Be sure to backwash or clean the cartridge filters when done to prohibit the algae from being able to re-enter the pool. To keep any algae under control be sure to keep the phosphate levels to under 200 ppb. Think of phosphates as food for the algae to grow because it is.

How To Kill Yellow Mustard Algae

Yellow mustard algae can be tricky to diagnose because it can appear to be what looks like pollen or it can make the pool look dirty. It is often mistaken for green algae because when you mix the colors yellow and blue you get green. So, the yellow algae in a blue pool can appear to be green in color.

When trying to figure out if you have yellow algae or not, you need to determine if the pool water is cloudy or not. If it’s not, then more than likely it’s not green algae. Green algae will make the water look murky and cloudy. If you brush the walls and it comes off and then comes right back in a few days then it’s not dirt or pollen. Dirt and pollen will settle to the floor and not get stuck on the walls of the pool. You have yellow/mustard algae it it comes back in a few days after brushing the walls and the water is not cloudy.

It really doesn’t make sense but yellow mustard algae can grow in a perfectly balanced pool and it’s more common in the warmer climates in the southern states. Keep in mind that it can still show up in the Midwest and North Eastern states. Pools can also be cross contaminated by using pool equipment from a pool that has algae and then used to clean another pool that is algae free.

It is recommended to use Sodium Bromide to kill off the yellow/mustard algae but is only good for one time. It can come back again whenever it rains. It’s a good idea to have the phosphates checked to determine if they are high (200+ ppb). If phosphates are high then use a phosphate remover after the algae has been removed from the pool. Be aware that phosphate removers can cause cloudy water but should clear up after a few days.

Swimming pools offer many benefits but can be a real pain the butt if you’re constantly fighting algae. You should have your phosphates checked regularly and when the levels are more than 200 ppb get them under control with a phosphate remover. This will prevent many algae blooms because it eliminates the food supply that algae needs in order to survive and grow.

Maintain your pool with proper water balance and brush, vacuum and clean the baskets and filters regularly. You should run the pool equipment at least 8-10 hours a day during the summer months. Being proactive is always better than trying to catch up with water treatments and can cost less in the long run.

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