How to Prevent Hot Tub Algae Formation

To defeat algae in your hot tub, you have to understand the tactics of your enemy. You have to think like algae and be like algae. Actually, it’s not even that complicated, but you can still make a good sport of abolishing those photosynthetic eukaryotic unicellular organisms collectively known as algae.

If you have a hot tub that has been balanced the right way, then algae is typically not an issue. But, if you allow algae to get a head start, it can be exceedingly difficult to completely eliminate. Remember: algae love your hot tub (well, in a figurative sense) almost as much as you do. Therefore, algae prevention is something you need to be vigilant about in order to prevent future issues.

This article will help you eliminate and prevent future algae growth in your hot tub.

How to Spot Algae

Algae comes in a variety of colors (typically green, blue-green, brown, and black), but algae is really just a broad term to describe a number of unicellular organisms that feed on sunlight and mainly use chlorophyll for photosynthesis. To properly treat your algae issue, you will want to identify the type of algae you’re dealing with. One of the best ways to do this is by identifying the algae by color.

Brownish algae — Algae that are brown or a brownish gray, usually indicate water with a heightened pH, so a product that decreases pH should be used. Although, high iron can also cause algae to take on a brownish hue.

Greenish algae — Greenish algae are usually fast growing (typically popping up overnight). These algae usually come about when water has heightened levels of magnesium or copper, and the greenish color is the algae interacting with these minerals. Usually the only symptom of a green algae bloom is that the surfaces of the hot tub shell will feel unusually slick or even slimy.

Bluish green algae — Bluish green algae are difficult to kill with chlorine-based sanitizers. You’ll also see this kind of algae form in bathroom tile grout and along the sides of bathtubs and showers. One of the best ways to treat this issue is by cleaning or replacing your hot tubs filters.

Brownish yellow algae — Another hard-to-treat form of algae are the brownish yellow (mustard-colored) varieties. The best way to treat these kinds is to scrub the surfaces of your hot tub, vacuum away any remaining debris, and then use your preferred shock chemical coupled with a type of algaecide product. After using the algaecide, be sure to scrub the surfaces again and keep your pump and jets running to keep the water passing through the filters.

Dark brown or blackish algae — Algae that have a blackish or deep brown hue are among the hardiest varieties, and therefore somewhat difficult to kill off. You may not think of algae as having roots since they are microscopic, but the black-colored algae have roots that reach deep into to the tiny pits of your hot tub’s shell. Like weeds, when the above-surface portions scrubbed off and chemically treated, new growths will sprout from the roots. To treat this type of algae, invest in a better filter and closely monitor your chlorine levels. In most instances, low chlorine is the “root cause” of this form of algae. Be sure to clean your filters regularly — especially after scrubbing the surfaces or using an algaecide.

Eliminating Algae

If you notice algae growing in your hot tub, the first thing you want to do is keep your jets going to circulate the water. Next, give your filters a deep rinse using a garden hose (the Filter Flosser does a great job at getting in between the pleats of your filters). Next, thoroughly clean the shell of your hot tub to remove any algae that may be hanging on tight.

Once algae has been removed from your hot tub, the next step is preventing a reoccurrence.

Preventing Algae Growth in Your Hot Tub

There are three main methods that you should use together to keeping your hot tub algae-free. These include balancing the pH of the water, balancing the alkalinity, and having the right concentration of sanitizers in your tub’s water.

Balance your pH — Ideally, your hot tub’s pH should be right around 7.5 or as close to that figure as possible. To help you achieve this goal, Master Spa Parts offers several products, including pH Plus (to raise the pH level), and pH Minus (to lower the pH level).

But, one issue of having a relatively neutral pH in your hot tub is that algae also thrive in the 6-8 pH range. But, without have a balanced pH of around 7.5, it can be extremely difficult to make sanitizers and alkalinity-raising products to work.

Keep water sanitized — Algae is a bacterium and one that can only grow in unsanitary conditions. If you plan on using a chlorine type of sanitizer, your level should ideally be right around 4 ppm, or if you are using a bromine-based system, your bromine level should be right around 3 ppm. Usually with these figures there is some wiggle room of +1/-1 ppm, but the closer you can bet your hot tub’s water chemistry to be on target the better results you can expect to achieve.

Maintain total alkalinity — Optimally, your hot tub’s alkalinity should be around 125 ppm (that’s “parts per million”) but really anywhere between 110-140 ppm should work. Note: Alkalinity can be related to pH, but it is a different measure of water quality than pH. One great product that can help with this is called "Alka-Rise," which is available in the Master Spa Parts online store.

When you are lowering or raising your hot tub’s total alkalinity, you should only apply a little product at a time, not trying to hit the target right away, but get it close. The reason being is that hot tub chemistries can react differently when various alkalinity-oriented products are introduced. So, try to get your alkalinity close, but don’t over-do the amount of product being added. Then, retest a half-hour to an hour later and add the necessary amount of sodium bisulfate (or other alkalinity product).

Note: When you research all the various hot tub products out there, you may come across some swimming pool products with similar formulations. But, these should never be used as a substitute and they do have the potential to cause significant harm to you and your hot tub.

Closing Thoughts

Your first reaction to seeing algae in your hot tub may be to throw a lot of chemicals at the problem, but in most cases, this isn’t the right solution. If you have algae issues with your hot tub ever year or so you may also want to bookmark this article so you can reference it in the future. With some patience, some scrubbing, and a bit of chemical balancing, you can enjoy many seasons of an algae-free hot tub.