How to Get Rid of Algae in Pool or Hot Tub

If you are a backyard pool owner, you don’t want your visitors to be disgusted with green pool water. The color of the water says a lot about your maintenance and sanitation efforts.

The same goes if you operate private pools for rental. You may lose valuable clients, and they may convince other potential customers to shy away from your business. How to get rid of algae in a pool or hot tubs?

For starters, regular pool maintenance and having well-proportioned water are the two basic safeguards from pool discoloration and health hazards. Having the correct sanitizer and pH levels are imperative too.

However, there are instances when unnecessary strain are put on your pool water:

  • Dead leaves falling on the pool’s surface from nearby trees can be problematic.
  • Unusually high volumes of pollen at certain times of the year
  • Consecutive days where the pool is crowded, distorting the balance of organic material volume in the water.
  • Added dust brought upon by windy seasons

Algae is a diminutive plant-like organism typically found in pools and tubs. Like any other plant, it needs cultivation in the form of organic materials in its surrounding.

Its favorite food for growth? Human fluids, of course. That’s the reason why it’s not ideal to have back-to-back pool sessions in days or hours, because algae feeds off of that extra sweat and urine. Meanwhile, dirt and dust trapped in pool or tub water provides algae with the element to immunize itself against lethal agents that can kill it like sanitizers.

Can algae harm individuals physically?

Obviously, no. These are too small and soft to impale the human skin. However, the bacteria feeding on algae discards are the ones that are harmful. When ingested or breathed, these could pose serious health hazards to anybody.

Algae Isn’t Always Green

It can come in darker colors. The darker the hue, the harder it is to get rid of (and kill) the algae.

Lime-colored algae (green)

This algae type is the quickest to form and grow simply because it thrives from poor filtration and sanitation. It usually starts as a blue or green algae floating on the water surface which make the pool look like stained.

It’s the easiest to get rid of. Manual brushing or algaecide, most of the time, is enough for it to crumble.

Mustard-colored algae (yellow)

This tight-fisted algae won’t go down without a fight. It usually grows on the pool side/wall that does not receive much sunshine.

Using normal sanitizer or chlorine levels does more harm than good. Because it isn’t strong enough to kill this yellow slime, it grows further. Before it becomes more stubborn, use a higher and stronger chlorine dosage to kill it outright.

Black algae (most stubborn one)

On a maintenance perspective, it hurts you in two levels: it has very sturdy protective coating that neutralizes most sanitizers while having deep roots that make it regenerate even if its visible portion is destroyed.

To completely eliminate black algae, you need to invest in an intensive pool brush, purchase huge amounts of chlorine shock (and have a great deal of patience).

Tip #1: Minimize organism presence by covering up

Imagine a wound that’s not properly patched up. More often than not, that wound is likely to get infected or aggravated by external agents.

The same goes for pools. The primary defense against algae formation is to put cover pools when not in use. Doing so prevents both common and random stuff from being in contact with pool water (e.g., dead insects, combs, bushes, etc.).

Remember that with less organism present, algae formation and growth are less likely too.

With pool covers, you won’t have to expend energy removing tree twigs or leaves each time they fall. Frequent use of pool vacuum and skimmer can also help in getting rid of surface nutrients that promote algae growth.

Also, it would immensely help if you can ask your guests or kids to take a quick shower before jumping right into the pool. Their accumulated sweat and dirt from a day’s work could be detrimental if your pool water takes those all in.

How costly are pool covers? It usually depends on the make, purpose, and functionality of the cover. Ordinary winter or solar pool covers could come as cheap as $45, while covers with safety and security features for its inhabitants could go up to $2,000 (because of its complex strapping systems).

What about automatic pool covers? Automatic covers provide the ultimate luxury and convenience. However, it can go up to $10,000, not to mention repair and replacement costs that can be triggered due to a specific gear breaking.

Tip #2: It starts with a holistic cleanup of the tub

Every time an algae outbreak occurs in your pool, it usually leaves residues that clog your filter. Make sure to deeply cleanse the filter, because failure to do so can lead to algae regeneration.

Also, make sure to sterilize pool skimmers and baskets. Frequently used skimmers tend to attract more organics that can build up over time, which will then serve as food for algae.

If you’re using sand filters, make an effort to at least replace them once a year as it may have lost its edge.

Tip #3: Chlorine shock as the standard algae killer

Killing algae with chlorine is the standard advice you’ll get from any reasonable pool owner.

Normally, algae clumps form when you seldom sanitize your pool, or if you do, you put relatively low levels of it on the water.

Chlorine shock is the process of introducing high chlorine levels to your pool water (typically up to level 10 ppm) to terminate contaminants such as algae.

Again, we’ve discussed how contaminants such as saliva, sweat, dead skin cells, urine, and even moist body lotion can promote algae growth. Chlorine shock breaks down the particles of such contaminants, so that those get removed from the pool water.

How often should you do chlorine shock?

At least once in the winter months. Also once in the summer if chlorine levels fall flat.

The good news is that you may never have to shock your pool – that’s if you consistently exercise sound water care (even in the summers and winters).

Earlier, we’ve mentioned how heavy and crowded pool use, rain, and windstorms can BOOST the growth of algae. As an added security and safety measure, shock your pool. This ensures that the water remains clear and health hazard free.

WARNING: Leave some time (typically overnight) before someone swims in your pool again after you did chlorine shock. Unlike non-chlorine treatments, a pool subjected to chlorine shock takes longer time to get back to normal and safe chlorine levels (i.e., 3-4 ppm).

What’s the recommended dosage?  

The standard is to pour twice the recommended amount of liquid chlorine. Now if the water appears to be foggier than usual, use three times of the amount. If it’s too dark that the top rung of the ladder is rendered invisible, put quadruple of the amount.

The best time to shock

During daytime, ultraviolet rays will render chlorine less effective because it breaks and dissolves it. Therefore, the optimal time to shock is during night time, so the party can be started once the sun shines.

Tip #4: Enthusiastically brush the floor and walls of your pool

At times, chlorine shock can only do so much. In case of a severe algal attack, you may need to manually brush your pool walls and floors first before applying high levels of chlorine.

Doing so makes it easier for the latter to penetrate, kill, and clear those stubborn clumps.

Aim to clear as much algae as possible. Make brisk strokes.

Don’t forget to use an appropriate brush make for your pool. For concrete pools, use steel brushes. Meanwhile, nylon brushes work optimally for vinyl pools.

What should you look for pool brushes? Performance and bristle durability. On top of that, make sure that the handle has extra strength to withstand hard strokes. Look for algae brushes that have quick lock handles for cleaning versatility.

It could come as cheap as $30, with premium ones (with added functionalities) costing up to $70-$100.

What are the critical areas to brush? These are the pool’s ladders, steps, corners, and splits. These are places where algae often accumulates; it can be crucial missing out on these areas.

Tip #5: Check for the pool’s pH and adjust when necessary

With the use of a pool pH test kit, you can check if your pool is infested with algae blooms. Normally, readings would show results of 7-7.6. However, if it goes above that, it’s a telltale sign of infestation.

The typical pH reducer is sodium bisulfate. Strive to bring down pH results to around 7.2-7.4 – optimal levels that allow your chlorine to be more effective in getting rid of algae.

After application, wait for a few hours before retesting the pool. Now if the pH levels normalize but alkalinity dropped, check the pH reducer’s label for instructions on how to bring it back up (i.e., normally 80-120 ppm).

Test strips versus droppers

Test kits can come in such two varieties. Results from paper test strips, however, are not always accurate. Treat it as a secondary option, and opt for droppers first.

Tip #6: Conduct pH retesting after 24 hours from the chlorine shock application

Re-examine the pool after 24 hours. It’s easy to spot deceased algae – it turned white and its remains float or stay in the pool floor.

Your aim is to check if chlorine and pH levels have changed. If the algae remains but chlorine levels rose to 2-5ppm, strive to make this level consistent for the next few days. If it rose but below 2 ppm, you need to conduct another chlorine shock in the night time.

Now, if there was no substantial change, it could be that the pool has overabundance of cyanuric acid. If this is the case, you have to shock several times, or deplete your pool partly.

Tip #7: Draw in dead algae

Yes, the pool filter can take care of this for you. However, an average filter can take up to several days before it can fully drain all algae remnants.

Instead, you can use a pool vacuum to draw in all the remains of dead algae. Notice that the water becomes clearer as you progress.

Clumping problem

Collecting all the dead algae can require a lot of effort, especially when it’s spread out. To save time, add a coagulant. This allows the remains to enter solid or semi-solid state, allowing it to clump together (which will save you time).

Tip #8: Thoroughly cleanse the filter

You should at least clean your pool filter 2-3 times annually. The pool filter is likely to function poorly if it’s blocked with dead algae.

In case of a cartridge filter, you need to utilize a high pressure hose in washing it. Such stress will completely eliminate debris that have accumulated over time in it. For optimal results, you can opt to apply liquid chlorine or dilute muriatic acid sparingly.

Staving Off Green Bath Tub Water

The main suspects for having green water in bath tubs is almost the same with large pools: algae infestation, low pH, low levels of sanitizer, and too much metal content.

For algae growth in tubs:

  • For every 500 gallons of spa water, spread on 1-2 ounces of tub algaecide. This is done when algae growth is minimal (to stop it and prevent recurrence).
  • Check your tub’s plumbing. This is usually where algae dwells when you can’t spot it on the tub shell. If this is the case, algae will continue to spread unless the plumbing is taken care of.
  • Consider the tub shell. Use non-foaming cleansers, but never go with household products (e.g., vinegar, bleach, etc.).
  • Like in pools, constantly check the tub water’s pH and total alkalinity. If needed, regulate to normal levels.

Having green water because of algae presence brings absolute inconvenience. Nevertheless, you have to do something about it to restore your pools and tubs back to its former glory.

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