How to Control Algae in your Marine Aquarium

A problem many aquarists encounter along their journey is the issue of too much algae in their tank. This is especially the case for beginners to the hobby, when they are trying to find the balance of maintaining a salt water tank.

If you are seasoned aquarist, you will know it is a perpetual balancing act of maintaining the right water parameters. The slightest change to your tank, and many of the key parameters can fluctuate, causing a chain reaction of issues to occur.

In this article we will be focusing on the issue of algae control. We will explore the types of different algae, causes of the problem and some remedies you can try when trying to keep this, what seems like an, unbeatable beast at bay.

Types of Algae

There are a number of different types of algae you will encounter in this hobby. Some are good and some not so good. And some types of algae are a personal preference – meaning some aquarists like the look of algae growing on their live rock and parts of the tank (such as Coralline Algae).

Brown Algae / Diatom Algae


There are quite a few types of brown algae. They are most commonly found in the Indo-Pacific Region growing on coral reef surfaces. They are not all bad as some of the types of brown algae can help reduce nitrates and controlling phosphate levels in your system.

Brown Algae is usually the first stage of the algae growth process and is the initial signs of other forms of algae beginning to grow.

Green Algae/Green Hair Algae


Similar to the Brown Algae, this Green Algae can commonly be found in the Indo Pacific regions of the Pacific Ocean. Since the brown algae is generally a sign that other types of algae are beginning to form, you will often see the algae change color. The difference with this type of algae is that you will start to see bubbles of gas forming between the hairs of the algae.

The usual causes of this type of algae is high nitrate and phosphate levels. By successfully managing your nitrate and phosphate levels, you will see a notable drop in algae production in your tank.

Red Slime Algae

Red slime algae is a very common problem amongst aquarists – and is, personally, a constant fight in my tank.

It is actually not an algae, rather a bacteria called Cyanobacteria. This type of bacteria uses photosynthesis to grow and release gases (including oxygen) into the atmosphere.

Given the above characteristics it doesn't sound like a problem at all right? I mean how can an oxygen producing slime be bad? The issue lies in the quantity of the slime. This red slime algae can inhibit the growth of your corals. It does this by blanketing all the surfaces with it's slime.

In face, my experience with red slime algae was that it almost killed my Green Star Polyp (GSP) coral! Any seasoned aquarist will know that the Green Star Polyp is an aggressive growing coral that if not carefully contained, can over-grow your tank and kill off other less aggressive corals by out competing for the live rock space. So for this type of slime to almost suffocate my Green Star Polyp shows how harmful this type of algae can potentially be.

Coralline Algae


Now this one is actually a popular type of algae that many aquarists welcome into their tank. It is a pinkish/purple colored algae that grows on any surface it can find. It isn't invasive or annoying at all. Corolline algae is a slow growing algae that aquarists consider aesthetically pleasing.

Most aquarists love seeing this in their tank, not only for the nice appearance, but it also indicates that the tank has a balanced and thriving environment. Almost like nature's way of giving reefers a stamp of approval.

Causes of Algae (and remedies)

When it comes to algae, it is generally safe to say the cause of any growth outbreak is the result of an imbalance in the tank.

Imbalances can be created by many factors, so let's explore some of the more common causes.

Excess Nutrients

A common cause of algae outbreaks is the presence of excessive nutrients in a tank. A common issue for individuals starting out in this hobby. It is easy to feel like you aren't feeding your fish or corals enough, so you over compensate by putting in too much food.

Even though you have the right intentions, by introducing too much nutrients (food) to your, you will unknowingly creating the perfect breeding ground for algae to flourish.


To help maintain a stable amount of nutrients in your tank, feed your fish and corals on a regimented feeding schedule – as opposed to feeding them because they look hungry. This way, if you are still experiencing algae blooms, you can cut down your feeding schedule methodically. It is also good practice to only feed enough food for your fish to consume in 15 – 20 seconds. If you see food in the tank after this period of time, maybe start reducing your portion sizes.

Incorrect Lighting

Another common cause for algae blooms. Keeping the lights on for too long can provide algae with the necessary environment to photosynthesize and grow at an exponential rate.

After a lot of experimenting, I eventually discovered this was my downfall. As much as I wanted to keep the lights on in my tank so I can see the wonderful aquascape and admire the fish darting in and out of the reef, I had to learn to limit the time for keeping the lights on.

Once I adjusted the light parameters, I noticed a dramatic decrease in the amount of algae in the tank.


As I mentioned above, by reducing the number of hours the light is on in your tank, you will limit the amount of algae growth. I find aiming for about 6 hours of white/daylight per day is a good target for controlling the algae growth.

It is handy to purchase a light that comes with a timer. Even though these types of lights can be on the expensive side, the reduction in hassles and maintenance of the tank is worth it's weight in gold.

Incorrect Water Source

Source: Unsplash

This one is similar to the excessive nutrients issue. However this is slightly different because you are introducing the unnecessary nutrients via the water source. Using sources such as your tap water will make controlling your nitrate and phosphate levels very difficult as it usually spikes when using an uncontrolled water source.


Only use Reverse Osmosis (RO) water when topping up your tank or performing water changes. By using RO water you know what you are introducing to your tank and be confident that you won't have any unnecessary nutrients in your tank.

Poor Tank Maintenance

A big culprit for algae blooms is poor tank maintenance routines. By not constantly monitoring your tank parameters and not performing enough water changes you are asking for algae to grow and cover your tank.


This one is easy. Just do better! If you are a serious aquarist you will have researched what you need to do to maintain a healthy thriving aquarium.

If you are one that tends to forget, use a notebook to annotate the parameters each time you check the water. Write down the dates of each water change. Get serious about building up a healthy and blossoming tank. Put it in your google calendar if you have to. Do whatever it takes to be an ethically responsible tank owner.


If you have an algae problem, hopefully by now you will have learnt how to combat the issue and have some actionable remedies you can try out to help control the outbreaks.

Algae can seem like an uncontrollable beast, however by applying a methodical, scientific process of elimination with the suggestions above, I am confident you will be able to overcome the algae blooms.

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