What’s the Difference? Harmful Algal Blooms and Controlled Algae Growth

Nick Sokol, PhD
4 min readSep 15, 2022


Harmful Algal Blooms (HABs) occur when there are extraordinary amounts of algae growth in a particular waterway. HABs can release toxins in the water that are harmful to humans and make consumption or use of a water body difficult. Pets, such as dogs, have been killed by blooms in various regions. Additionally, natural aquatic wildlife such as fish and plants, are often killed off during the occurrence of a HAB which can create ecosystem damage in the long term. A lot of people often ask the question, “why should I grow algae if it’s causing all this damage in the wild?” Well, there’s a big difference between the algae we grow in a controlled environment and the runaway algal blooms that can occur in the wild. This article will hopefully clear up the difference between these two occurrences.

How do Algal Blooms Occur?

HABs tend to occur when conditions for algae growth are overwhelmingly positive. Variables that influence HABs are temperature, nutrient concentration, and wind/current flow. Temperature influences the algae by providing a comfortable environment that enhances growth. Warmer water temperatures allow algae cultures to move more efficiently and absorb more sunlight instead of sinking to the bottom of a water body. Nutrients are absorbed by algae in the warmer water and allow them to continue to grow and multiply. Wind/current flow provides either enough mixing to disperse the algae — preventing them from growing, or just enough to keep them on the surface of the water and allow them to continue growing. Once the algae have sufficiently captured a large surface area of a body of water, an algal bloom has officially begun.

Can an Algal Bloom Occur in a Bottle?

In short, no, an algal bloom cannot occur inside of a bottle or container, or any controlled environment for that matter, but if the right conditions are provided it could happen. Within a bottle or container, such as a fish tank, there’s typically adequate mixing that prevents algal blooms. An aerator or pump is used to keep water circulating and this typically prevents algae from building up on the surface and rapidly multiplying. Nutrients are also much more controlled in a controlled growth environment. Unlike in nature…

Nick Sokol, PhD

I write about Sustainability, ClimateTech, Entrepreneurialism, Technology, and Software Engineering.