How to Get Rid of Algae in Hydroponics (9 Easy Ways)

Having a build up of algae in your hydroponic system can cause major headaches. It’s inevitable that some degree of the yuck stuff will form amongst your plants and keeping it to a minimum is crucial. Once algae begins to grow, it’s tough to get rid of it completely, so it should more so be closely managed.

How to get rid of algae in hydroponics
How to get rid of algae in hydroponics?

Too much algae can reduce the amount of oxygen and nutrients in the water and grow medium. As algae is an organism that feeds from the same source, it will pretty much steal them from your plants. This in turn will decrease overall plant growth.

Furthermore, it can have a huge impact on the pH of your whole system. There is hope though. Some methods can be utilized to keep algae to a minimum and restrict further spreading. These include reducing the amount of sunlight that your nutrient solution and growing medium receives. Also keeping drippers and emitters as clean as possible can assist with cutting down any unnecessary algae build up.

I will look into what exactly is algae before explaining how to get rid of algae in hydroponics.

What is Algae?

What is Algae?
What is Algae?

Algae is basically a plant without the roots, stems, leaves and a specialized multicellular reproductive structure. A.K.A the ‘weeds’ of hydroponics. They have the uncanny ability to develop under the exact same conditions as a plant. Similarly, they require the same 3 basic elements as most other vegetative forms. Sunlight, water and nutrients. They don’t even need much of the 3 elements to begin their process either. A small amount of each is ample to begin their process.

Therefore, a hydroponic system has everything that algae requires to not only form, but also to grow and thrive. Sometimes even take over! That is of course if you don’t see the warning signs early on. Unfortunately the warning signs are literally seeing the algae start to build up. 

Algae can form in a range of different colors and can have multiple defining characteristics within a hydroponic system.

It’s colors can include:

  • Green.
  • Black.
  • Brown.
  • Red Blue/Green.

It’s characteristics can include:

  • Bubbly.
  • Slimy.
  • Furry.
  • Stringy.
  • Sticky.
  • Hardened.
  • Clingy.
  • Smelly.

Now that we have a clear about algae, let’s find out how to get rid of algae in hydroponics.

How to Get Rid of Algae in Hydroponics (9 Best Ways)

There are some pretty effective ways to help to reduce the impact of algae. Some methods are implemented whilst planning and others are more problem, reaction, solution based. Here’s 9 different approaches that you can apply to your system 

9 Ways to get rid of algae in hydroponics
9 Ways to get rid of algae in hydroponics


It’s not easy to find a way to restrict algae without harming your plants at the same time. They both require the same elements to grow. Implementing shading is a less damaging way to help reduce algae growth. It is also probably the most simple method to implement.

When setting up your system,  you can wrap your reservoir or hydroponic nutrient solution container in black plastic or even paint it in a dark color. Anything that is dense enough to reflect light is ideal.

Aluminum foil, dark coloured polyether or even multiple layers of brown paper. This measure will prevent light protruding into the tank. By excluding the light from reaching the nutrient solution, algae won’t be able to grow.  

UV Filtering

UV filters can be worth investing in to automate the process of killing algae in your tank. They compliment the water filtration system. As old recycled water flows in, the UV filters pick off and kill the algae and/or other microorganisms as they enter the system.

Their only drawback is the upfront cost, including installation as well as maintenance. Otherwise, they can be very effective pieces of equipment. 

Regular System Cleaning and Sterilization

Cleaning and sterilizing your system manually requires a bit more elbow grease. As a result though, the finished product is more satisfying knowing that you can potentially scrub every nook and cranny.  The process should only take a few hours. If consistent maintenance is applied as soon as you notice early signs of algae, it should be a lot easier to stay on top of things. 

Giving your system a good clean out can be completed in 2 steps. Removing existing nutrients and then flushing it out with a good quality cleaner and sterilizer solution. Let’s have a look at how to perform this task in as straightforward steps as possible.

  • As a general rule, when doing any type of cleaning, water change over, nutrient replenishment, etc, ALWAYS turn off the power supply to your hydroponic equipment. Better still, unplug it just to be on the safe side.
  • Drain out all water and nutrient solution. Depending on the type of system you have, this method could vary. Usually though, it’s as simple as disconnecting the drainage pipe and letting it all run out. Otherwise, you could have a tap/vent installed where you open that up and let the solution drain out. Obviously make sure that it’s running somewhere where you want it to run, not directly on to the floor for example.
  • Disconnect all individual parts to ensure access whilst cleaning. Keep in mind that some parts of the system can be reached without disconnecting but other areas will be harder to reach and scrub out. 
  • It’s advised that you create a good quality cleaning/sterilization solution. You can either use something along the lines of Hydrogen Peroxide 35 V/v concentration or another top choice is Hydroguard. 3 mL of either of these 2 solutions to 1 gallon of water is the perfect ratio. You could  also opt to use an unscented neutral bleach using a 1:100 ratio. 4 mL of this solution to 1 gallon of water is optimal.
  • Once you have your cleaning/sterilization agent, you’re basically cleaning out the whole system from top to toe. If you have a high pressure hose, they are going to help you blast away any more thick gunky stuff. If not, the process will take a bit longer. When scrubbing, start with the tanks and pots as they are usually larger and require more time to dry out. Then scrub the pipes including the joins and taps/vents thoroughly. Lastly, move onto the tools and or equipment that are used to tend to the system. They can also produce algae and home a colony of algae if not sterilized properly. 
  • Once you feel that you are satisfied, reconnect all parts so the system is whole again. Give the system a good flush 2-3 times with water (preferably high pressure but not necessary) This will ensure that any remnants of the cleaning agents are completely washed out.
  1. Allow the sunlight to dry all parts out before replenishing the nutrient solution and getting your system back up and running again. 

Grapefruit Seed Extract

Another known organic method is by using the seed extract from grapefruit. Grapefruits have ant parasitic and antibacterial properties. These properties help with the fight against humic acid which in turn helps to erode any algae build up.

5-10 drops of the extract per gallon of water is all you need to help your system stay on top and get rid of algae. The beauty of this stuff is that because it is organic, it has no negative effects toward your plants. In fact, it can boost yield production by utilizing the extra nutrients provided. 

Barley Straw Rafts

Again with another organic practice, this time by using barley straw rafts. Funnily enough, in the 13th century, farmers noticed that bodies of water that had bales of barley straw in them, had significantly less algae build up in them. This is where the concept arrived from.

Now days, though, it comes in the form of pellets. These natural gems have the ability to release a specific chemical into the system’s nutrient water supply.

As it releases the chemical, it starts a process called aerobic decomposition. During this process, the chemical eats away at the algae which as a result leaves the system with a lot less of it in the long run. It’s more of a slower process though as the barley is dense and takes a little extra time to decompose.

This method is more suited to larger, more deeper systems which allow the rafts room to take effect. 

Humic Acid

Humic acid is a chemical that can be used to help neutralize both acidity and alkalinity. As a result, this assists in pH value regulation. One of its greatest feats though is its ability to improve and optimize water and nutrients that a plant receives. Humic acid will oxidize the algae which keep them from multiplying as fast. 

Using Commercial Algicides

Commercial algicides are pretty much large scale chemical disinfectants that target algae. They are often used in commercial swimming pools via chemical feeders, suppliers and probes to restrict any growth. They can also be used in hydroponics and aquaponics systems and won’t harm either the fish or plants if used in the correct manner. 

Changing hydroponic nutrients (without phosphorus)

If your system has a high amount of phosphorus, the amount of algae will increase as a result. You can change out your nutrients in your system using specific solutions that have levels of phosphorus that can help a plant but on the other hand, not allow algae to grow.

It depends on the amount of Nitrogens (N) and Phosphorus (P). Choosing nutrients with lower amounts of the 2 promote healthy plant growth and halt algae production in a hydroponic system. There are a great range of products that can give the required results including the Advanced Nutrients pH Perfect Grow, Micro, Bloom 4L varieties. Again, it all depends on the result that you are after.

Keeping the temperature low

This can be achieved in multiple ways. The obvious would be to keep the system away from any warm areas or areas like around heaters or motors that produce heat for example. Also spots that may get way too much heat from excess sunlight can be problematic.

Some other methods can include shading as mentioned a little earlier and also setting up fans to move the warm air around. Adjusting the water temperature is the first port of call though. Maintaining the temperature of the water at an even 40°F (4.4°C) will reduce most algae in its forming phase.

This temperature will be totally fine for the rest of your crops to continue on their merry way. Anything over the 57°F range (14°C), is adequate for the growth of certain types of algae.

Read on to know about how does algae enter the hydroponic system, so you can execute better what you have learned about how to get rid of algae in hydroponics or even prevent it.

How Does Algae Get Into a Hydroponic System?

Algae are ultra durable and stealthy. This makes them almost impossible to stop as they make their impact. They get into your system through microscopic airborne spores. Consequently, it’s pretty hard to actually see them latch on and establish themselves.

Algae benefit from the system’s warmer temperatures. It’s perfectly humid for them to latch on. As a result, they begin to gorge on the welcoming platter of nutrients and their ample supply of water. Of course, the cherry on top is the convenient supply of light. It’s the ultimate growth cocktail.

They aren’t selective either. From growing medium, roots, water, utensils, the whole system can become caked in the stuff in a very short period of time. If it isn’t treated at the first site, a lot of issues can occur. The best methods to help reduce algae build up are shading an UV filtration.

Here’s interesting video I found on YouTube to understand the impact of algae on hydroponic system:

How Does Algae Affect a Hydroponics System?

Algae affects a hydroponic system by depleting and fluctuating oxygen levels. Furthermore, it depletes the amount of nutrients within the system. Additionally, it causes issues with pH levels and can create toxins which are tough to combat. Let’s have a look into how these factors can cause problems for your hydroponic system. 

How Does Algae Affect a Hydroponics System?
How Does Algae Affect a Hydroponics System?

Oxygen depletion and fluctuation

Algae creates problems with the system’s oxygen supply on 2 fronts. 

Firstly, during the day, algae makes its own oxygen source by splitting water molecules using photosynthesis. As a result, it doesn’t rely on anything else for its supply. It hums along doing its own thing. When it’s dark though, algae stops its photosynthesis process. It needs light to continue, right?

This sees that it consumes the environment’s oxygen but doesn’t produce any of its own, leaving the system with less of the precious chemical element. This means that there is less for your plants. Less oxygen for your plants can severely stunt their growth and in worse cases, cause them to suffocate and wipe them out!

Therefore, the fluctuation of the oxygen within the system can be tricky to gauge. You could be trying to compensate for a certain amount but misjudge that it requires either less or more!

Nutrients Depletion

As algae multiplies, it depletes the nutrients which would usually be designated for the vegetation that is being produced. It will want to enjoy the same food supply as your plants. 

This is why it’s important to try to get rid of the algae at the first sign of appearance. Algae will also essentially turn the nutrient water into a thick kind of gluggy, syrup type texture. 

It won’t necessarily cause physical harm to your plants but will more or less clog up your system that it grows in. As a result, it will make the nutrient supply more concentrated, deeming it less effective.

pH problem

Algae can cause pH swings which can often be misleading. As algae consumes carbon dioxide during the daytime, it’s also removing what is called a ‘weak acid’ from the system. This ‘weak acid’ can be seen to sit within a specific range on the pH scale. As it is removed, the pH increases by a few points on the scale.

Usually, when you notice that the pH is too high or too low, you can adjust it manually. When the pH levels fluctuate via infiltration of algae though, adjusting it based on what you read could throw the whole environment out of sync. You could be taking a reading during a certain time of day when the pH is lower then taking it again later on when it is higher. It’s knowledge that is formed over time. 

Toxin Issue

There are certain algae species that when grown within specific environments can release harmful toxins as they decompose. As a result, these decomposed algae can become a food source for fungi that can go on to produce potential diseases. Consequently, this funghi has the ability to wreak havoc on your plants as the level of them increases.  

Other Articles On Hydroponics You May Find Useful If You are a Beginner: Do Hydroponics Need Sunlight?Does Pot Size Matter in Hydroponics?Can You Plant Hydroponic Basil In Soil?Is PVC Safe For Hydroponics?

Frequently Asked Questions (FAQs)

01. Is algae good for hydroponics?

It’s inevitable that some form of algae outbreak will form within your hydroponic system. It’s a problem if it starts to take over everything because you’ll pretty much have to reboot your system. (Clean out and sanitize) This isn’t a huge deal but more of a setback in other words.

The biggest problem is when it starts to grow wild during a plant growth cycle and you possibly lose all of your hard work and effort. The best chance at avoiding bigger issues is to plan and prepare. A little bit of algae however isn’t the end of the world as long as it is controlled. 

02. Does algae cause root rot?

There is a process that algae goes through when they break down that as a result can damage the roots of the plants within a hydroponic system. As the algae bloom, die then decompose, they clear away dissolved oxygen from the hydroponic system.

As a result, the plants require more dissolved oxygen but can’t get enough so they end up suffocating. Consequently, root rot takes hold.


There are many ways regarding how to get rid of algae in hydroponics. Some require planning beforehand and some can be added at the first sight of algae. As a worst case scenario, sometimes it’s better to disconnect the whole system, give it a lot of TLC (clean it out) and set it back up like new.

There’s no easy way as algae can and will strike in almost every system. Being on the front foot is key here! We hope that this article has helped to bring light to a topic that is often not thought about.

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