By Luke Sumpter Reviewed by: Miguel Ángel Garcia

How to keep algae out of your grow


Algae boast the status as one of the most important organisms on Earth. The aquatic lifeforms produce up to 50% of all oxygen on the planet, and they serve as food for the majority of aquatic life. Despite their vital role, though, algae can quickly become a problem for growing cannabis.

Moisture-loving algae quickly secure a foothold in hydroponic grows, although they can find their way into any growing medium.

Once established, they pose multiple threats to cannabis plants. Along with obstructing oxygen uptake, they offer a breeding ground to pathogens, and they can become a cosy home for pests. Below, you’ll learn how algae grow, why you don’t want them in your grow space, and what to do when they show up.

How Do Algae Grow?

Ultimately, algae require three primary factors to grow and thrive:

  • Moisture
  • Light
  • Essential nutrients

These environmental requirements are also the building blocks of every hydroponic and aeroponic growing system. The lifeforms become particularly problematic in those systems when they receive more light, freeform nutrients, and access to root systems.

However, they can also be found in other growing mediums like coco fibre and soil. That being said, with denser mediums like the latter, algae can only thrive on the surface.

Algae is almost impossible to avoid when growing hydroponically, especially when utilising organic nutrients and living water with beneficial bacteria. High levels of nitrogen, potassium, and phosphorus—key to cannabis plant development—also fuel algal blooms.

Despite their fundamental role in ecosystems and fascinating behaviour, algae are surprisingly simple lifeforms. Just like cannabis plants, these photosynthetic organisms require light to generate energy to survive, yet they lack leaves, stems, and roots.

Algae first enters hydroponic systems through microscopic airborne spores. Once these small packages of DNA land in a compatible environment, they start to develop into fully-formed cells. Algae reproduce through a process known as mitosis, during which the nucleus divides and produces genetically identical daughter cells.

When mitosis really gets going, algae begins to take over hydroponics sets ups. After proliferating enough, the lifeforms can start to cause several issues that put growing operations and yields at risk.

How Do Algae Grow?

Will Algae Kill My Cannabis Plants?

Left unchecked, algae can cause significant damage to cannabis plants. Algae themselves don’t directly attack cannabis, though. Rather, along with suffocating plants and equipment, they cause harm by attracting pests and pathogens that eat and infect cannabis.

Algae Suffocate Plants And Clog Equipment

As algae proliferate on the water’s surface, it eventually forms large clusters around hydroponic roots systems. The organisms cling to roots as a supportive structure and quickly make their way up, especially if you use organic materials like rock wool. If left to grow out of control, algae disturb root function and impair nutrients abduction and oxygen uptake. They don’t just block roots from taking in oxygen; they steal the essential molecule for itself.

Algae take in carbon dioxide and put out oxygen during photosynthesis. However, these roles switch during the night. Without light, algae begin to transpire and uptake oxygen, leaving your plant with a minimized supply—potentially suffocating the roots. As algae take in oxygen and release carbon dioxide, they cause carbonic acid to accumulate in the water. This causes a significant drop in pH. Wild pH fluctuations occur when algae switch between either of these gases, disrupting optimal pH balance.

Algal growth doesn’t limit itself to the root system of cannabis plants. Before you know it, a vigorous bloom can work its way into pipes, filters, and external water reservoirs. Algae can also block air pumps, impeding ebb and flow systems & potentially causing flooding in automated systems when left unattended.

Algae Attracts Pests That Munch On Weed Plants

Thankfully, algal cells don’t possess mouthparts that chomp through stems, leaves, and roots. However, they do provide an ideal habitat for others that create water at the mouth at the sight of cannabis. These include:

  • Midges
  • Aphids
  • Nematodes
  • Cochineals
  • Fungus Gnats

All of these pest species feast on different parts of cannabis plants, including the roots and leaves. When these structures take too much abuse at the hands of these critters, key physiological functions become compromised. Leaves with too many holes fail to photosynthesise properly, and damaged roots won’t fulfil oxygen and nutrient demands.

Algae – A Hotbed of Plant Pathogens

If oxygen theft and pests weren’t good enough reasons to warrant banishing algae from your grow room, pathogens will be. Various species of fungi also thrive in moist and stagnant conditions, including:

  • Fusarium
  • Pythium
  • Alternaria
  • Verticillium
  • Septoria

These species can cause several different diseases to arrive, including root rot and leaf spot disease. Algae also help some of these pathogens get a foothold, even hurting plants that thrive above the surface.

Algae – A Hotbed of Plant Pathogens

Symptoms of Algae Build-Up on Cannabis Plants

The symptoms of algae are widely varied. The manifestation of plant ailments will depend on exactly how the algae affect your crop—directly or indirectly. The primary symptoms of an algae infestation include:

  • Oxygen deprivation (wilting, distorted growth, yellow leaves, dropping leaves).
  • pH fluctuations (stunted growth, leaf spots, wilting, nutrient deficiencies).
  • Pest infestations (visible insects around the leaves, holes in leaves, yellowing).
  • Fungal diseases (wilting, browning, black/brown rotted roots, cankers, oozing sap).

How to Spot Algae

Before we dive into techniques to prevent and tackle algae, you should know exactly how to identify it.

It often appears in the form of a green film on the surface on your reservoir and on the interior of your pumps, tubes, and pipes. They can also display shades of brown, gold, red, and black.

Despite it being visually obvious, growers can also detect algae with their nose before they lay eyes on it. If you detect a mouldy or earthy smell while walking past your grow, you should look for algae forming.

How to Prevent and Manage Algae

As an inevitability in hydroponic growing, working to prevent algae will only go so far. Probability dictates that the organism will show up at some point, especially in organic living grows that aim to accumulate microorganisms. Luckily, small algal infestations will do little to impact the health of your plants, and there are steps you can take to minimise their growth.

Keep Your Equipment Blacked-Out

As the old saying goes, prevention is better than a cure. Taking steps to reduce algal growth will save you more work in the long run.

Because algae require light to grow, establish, and proliferate, depriving them of this life source does wonders to keep their numbers down. To keep them in the dark, follow these tips:

  • Go for thick, black plastic when making or purchasing a reservoir and pipes
  • Select black tubing (as opposed to transparent)
  • Use spray paint to black-out tubs and jars if using the Kratky method

Blacking-out all pieces of equipment and surfaces that contact water and light will give you a great head start against algae from the start.

Maintain An Optimal Temperature Range

Just as it thrives on light and nutrients, algae also adore warmth. The organism will multiply much faster and more efficiently in warmer water. However, your plants will be affected if temperatures drop too low.

Aim to keep the water temperature between 21-23°C to fend off algae while keeping your plants happy. You can track water temperatures and keep them consistent using thermometers and hydroponic heats and coolers.

Maintain An Optimal Temperature Range

How To Treat An Algae Infestation

Now that we’ve covered the most effective preventative measures, let’s take a look at how to beat algae down once it makes an appearance.

There are several options growers have when it comes to getting rid of algae. Some of them are ideal for sterile growing, whereas others are friendly to living organic growing methods.

Hydrogen peroxide sends algae running.

Mix 3ml of H₂O₂ (3%) with one litre of water and give all surfaces a good scrub down. As a highly volatile and water-soluble chemical, H₂O₂ works to destroy the cell walls of algae and remove them from the growing space.

Utilize some grapefruit seed extract.

Use it as a natural alternative when scrubbing down reservoirs, tubes, pipes, and surfaces. The phytochemicals in this extract help to remove algae quickly.

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Privacy Policy - Royal Queen Seeds

To ensure a safe online environment and guarantee adequate data protection, we strictly comply with all legal requirements. In this privacy statement, we provide information about how and for what purpose data is collected, safety measures, storage periods and contact details.


COMPANY NAME: SNORKEL SPAIN, SL (hereinafter ROYAL QUEEN SEEDS)

C/ Vilar d'Abdelà, 5 (nave 1) CP: 08170 de Montornès del Vallès

+34 937 379 846

support@royalqueenseeds.com


The present Privacy Policy sets out the terms on which we will treat personal data at ROYAL QUEEN SEEDS; this includes any personal data collected through our website https://www.royalqueenseeds.com/ as well as any other data we process in the course of our business activities.

ROYAL QUEEN SEEDS collects the following personal data for the purposes listed below:

SECTION 1 – PERSONAL INFORMATION WE COLLECT

1.1 Account purchases

Account purchases can only be made if you are in possession of a personal account. When you create an account or purchase something from our shop, as part of the buying and selling process we collect the following personal information that you provide to us:

This information is required for delivery. In addition, when you browse our shop, we automatically receive the Internet Protocol (IP) address of your computer. Based on this information, we can optimise your online experience and at the same time protect our online environment.

Purpose of data collection

We collect and store account-related data for the following purposes:

(a) to carry out obligations arising from any contracts between you and us, and to provide you with information, products and services that you may request from us;

(b) to set up, manage and communicate with you about your account and your orders;

(c) to conduct market research and analysis;

(d) to confirm your age and identity, and to detect and prevent fraud.

1.2 Newsletters

With your explicit permission, we may send you newsletters about our shop, new products and other updates. We send newsletters based on your explicit consent. In the event that you purchase a product, and in accordance with current regulations, we may send you commercial communications in accordance with the legitimate interest of our company, always about products or services similar to those you have purchased or contracted. In any case, you may exercise your right of opposition through the channels announced in this Privacy Policy. The following information is collected in relation to the newsletter:

We do not need to know the sex of the person in order to send the newsletter (data minimisation: by law we must ask for data that is strictly necessary to provide the service, and in this case knowing the sex is not necessary to send the newsletter).

Purpose of data collection

The data collected is used to:

(a) personalise our emails, including your name and gender;

(b) provide gender-specific content.

You can withdraw your consent at any time by using the link provided in the newsletter or the contact information provided in section 2.

1.3 Customer service and contact form

In order to provide appropriate support, our customer service employees have access to information related to the account. Consequently, their support will be highly effective and friendly. The data provided in our contact form is used by our CRM provider, SuperOffice. We will only use your details to respond to your message.

SECTION 2 – LEGITIMATE INTEREST

If you have purchased any of our products, please note that we may process your personal data for promotional purposes, based on Royal Queen Seeds' legitimate interest only to offer you products or services from our company and about products or services similar to those you have purchased. You may exercise your right to opt out of future messages by the means set out in this Privacy Policy or through any notification you receive.

2.1 How do you withdraw consent?

If you change your mind, you can withdraw your consent for us to contact you for the purpose of collecting, using, or disclosing your data at any time by reaching out to us at: support@royalqueenseeds.com.

SECTION 3 – DISCLOSURE

We may disclose your personal information if we are required to do so by law or if you breach our Terms of Service.

SECTION 4 – HOW LONG DO WE KEEP YOUR DATA?

At Royal Queen Seeds, we will not retain your data for longer than is necessary for the purposes described in this Policy. Different retention periods apply for different types of data; however, the longest period we will normally hold any personal data is 10 years.

4.1 Account information

Data relating to the account remains relevant for as long as the consumer is in possession of an account. Therefore, the data remains documented for as long as the account exists. When our customers delete an account, the associated data will be deleted within a reasonable period of time. Requests regarding the inspection or correction of stored personal data or the deletion of an account can be sent to support@royalqueenseeds.com.

4.2 Newsletters

In the event that you give us your consent to inform you about our products or services, we will keep your data until you express your wish not to receive any further communications from us. However, we regularly (every month) carry out a relevance check. Registered customers (and their personal information) will be deleted whenever customers do not reply to our request. In addition, our newsletter mailing has an opt-out feature. Consumers can withdraw their consent by using this opt-out feature.

SECTION 5 – COOKIES

Cookies are small information files that notify your computer of previous interactions with our website. These cookies are stored on your hard drive, not on our website. Essentially, when you use our website, your computer displays its cookies to us, informing our site that you have visited before. This allows our website to function more quickly and remember aspects related to your previous visits (such as your username), making your experience more convenient. At Royal Queen Seeds, we use two types of cookies: functional and analytical.

5.1 Functional Cookies

Functional cookies are used to enhance your online experience. Among other things, these cookies track what is added to your shopping cart. The use of these cookies does not require prior authorization.

5.2 Analytical Cookies

Analytical cookies are used for research and market analysis. The data collected with these analytical cookies is anonymous, making it unusable for third parties. The use of these cookies does not require prior authorization.

SECTION 5 – THIRD-PARTY SERVICES

Third-party services are required to conduct transactions and provide our services. In general, the third-party providers we use will only collect, use and disclose your information to the extent necessary to enable them to perform the services they provide to us.

However, certain third-party service providers, such as payment gateways and other payment transaction processors, have their own privacy policies regarding the information we must provide to them for your transactions.

We encourage you to read the privacy policies of these providers so that you can understand how these providers will handle your personal information.

In particular, certain suppliers may be located or have facilities located in a different jurisdiction than yours or ours. Therefore, if you choose to proceed with a transaction involving the services of a third party, your information may be subject to the laws of the jurisdiction in which that service provider or its facilities are located.

Once you leave our website or are redirected to a third-party website or application, you are no longer governed by this Privacy Policy or the Terms of Service of our website.

Web analytics service (anonymous data)

On this website we have integrated an element of a web analytics service (with anonymisation functionality). Web analytics can be defined as the gathering, processing and analysis of data about the behaviour of visitors to websites. An analytics service collects, among other things, data about which website a person came from (the so-called referrer), which sub-pages they visited or how often and for how long they visited a sub-page. Web analytics is mainly used for website optimisation and for a cost–benefit analysis of internet advertising.

Courier service

To complete deliveries we use a courier service. This courier service carries out the delivery between our company and the consumer's home. To complete these logistics, the company requires access to the consumer's name and address information.

Mailing service

Royal Queen Seeds uses a third-party mail service provider to send its newsletter. This provider has access to limited account information related to opt-in consent (e.g. email address).

Marketing services

Royal Queen Seeds has the support of a company that specialises in marketing and communication activities. Their access to personal information is very limited and mostly anonymous.

Payment services

At Royal Queen Seeds we use external payment services to handle our transactions (e.g. credit card payments).

SECTION 6 – SECURITY

To protect your personal information, we take reasonable precautions and follow industry standard best practices to ensure that it is not inappropriately lost, misused, accessed, disclosed, altered or destroyed.

If you provide us with your credit card information, the information is encrypted using secure socket layer technology (SSL) and stored using AES-256 encryption. Although no method of transmission over the internet or electronic storage is 100% secure, we follow all PCI-DSS requirements and implement additional industry standards that are commonly accepted. Information related to the account is protected with a hashing method. This method transforms the information into a generated hash. As a result, confidential information is protected and invisible, even to us. In addition, our databases are exceptionally protected against unauthorised access. For example, access to the database is only possible and permitted via approved IP addresses (e.g. from Royal Queen Seeds headquarters). Other attempts and addresses are rejected at all times.

Furthermore, data is anonymised as much as possible, so it cannot be directly linked to a specific consumer. With this data, however, we may be able to carry out market research and analysis. In addition, the third parties concerned (e.g. mailing service) are examined prior to our collaboration, comply with the GDPR from the EU and receive a processing agreement. Within Royal Queen Seeds, employees are assigned different access permissions. Specific permission provides access only to information that is strictly required to perform a task. Digital security measures are subject to change and must meet high requirements to ensure the safety of online customers. That is why, at Royal Queen Seeds, we appoint a security officer. Regular verification and improvement of security measures (where necessary) are part of the role.

SECTION 7 – CHANGES TO THIS PRIVACY POLICY

We reserve the right to modify this Privacy Policy at any time, so please check back regularly. Changes and clarifications will be effective immediately upon being published on the Website. If we make substantial changes to this policy, we will notify you here that it has been updated so you will know what information we collect, how we use it and under what circumstances, if any, we use and/or disclose it.

SECTION 8 – YOU HAVE THE RIGHT TO: