Saltwater Algae Control: Green Algae 2

Share This On


Green algae definitely does not win any popularity contests among aquarium enthusiasts. It’s probably the most common form of algae that gets into your aquarium. It makes your aquarium dirty, looks disgusting and is pretty fast at absorbing essential elements required by corals and other plants in your aquarium making it a pretty big problem to deal with.

Once it starts growing in your aquarium it can be pretty hard to control its growth if action isn’t taken promptly and once this happens, you’ll have a big task at hand to clear out the existing green algae and also prevent its further growth.

Being such a recurring problem among fish hobbyists it’s important to address the issue and to do so in a manner so that it doesn’t adversely affect the aquarium’s ecosystem.

Green Algae

Green Algae

Along with being the most common type of algae found it also is the most problematic of all the algae because of how fast and easily it spreads.

There are numerous causes of the growth of green algae in aquariums and they don’t need an invite to start growing uncontrollably. Thus, it is very important to keep a close check on the water’s parameters such as the nutrient levels, lighting conditions and pH levels.

This post is part 3 of the Saltwater Algae Control series, you can check out the rest of the series here:-

What Is Green Algae?

With over 7,000 known species, green algae or hair algae as it’s known is one of the first and most common of the algae intruders in aquariums.

They are as the name suggests, green in color, although their color varies in shades of green right from light green to dark green. It looks like a green velvet like carpet that’s growing in your aquarium. Green algae primarily consists of short hair like structures that grow in clusters.

They can be quite a handful to deal with once they find a way inside your tank and can spread very rapidly which can cause havoc in the balance of the marine ecosystem in your aquarium.

Advantages Of Green Algae


Well, it looks like a velvet carpet, but uh… nothing here really.

Disadvantages Of Green Algae

1. Deprive Corals From Nutrients

Green algae are real pests that can suck up the nutrients in the water leaving absolutely nothing for the corals in your aquarium.

The corals in the aquariums play a very big role in the maintenance of balance of the marine ecosystem in the aquarium and with the presence of green algae they can’t thrive.

2. Ruins Your Good Looking Tank

Although I stated that the algae can look similar to a green velvet carpet, it doesn’t look pretty really. It spreads to different corners of your tank covering everything in green, it’s also very icky and probably not the prettiest thing to have in your tank.

Hard work gone down the drain?

Hard work gone down the drain?

You go to various lengths in order to keep your tank clean and nice looking but the green algae can completely ruin this.

3. Covers The View Of Your Fish

Green algae can start growing on your tank walls and cover the view of your beloved fish. We don’t want those nasty things to be covering what you really want to be seeing, do we?

4. Hard To Get Rid Of

Scrubbing green algae is hardly effective and many algae eating fish also refuse to eat green algae making it very tough to tackle this nuisance.

Causes For The Growth Of Green Algae

Probably easier to grow than a cactus, green algae barely needs any mistake on your end for it to get into your aquarium and pretty much take it over (alien spaceship style).

On a more serious note though, there are a number of reasons because of which green algae grows which is why it is the most commonly found algae in aquariums that hobbyists encounter on a regular basis. Let’s take a look at some of the main reasons that causes a green algae outbreak in your saltwater aquarium:

1. Excessive Lighting

The life of any plant hinges onto the fact that it needs light in order to carry out photosynthesis which is key to their survival. Although you do require a certain amount of light for the other organisms in your aquarium you need to restrict it between 8 to 10 hours a day so that there’s just enough light for the marine life but not enough to support algae growth.

Control your lighting

Control your lighting

Also, if you’re using artificial lighting, make sure to set a timer so that the lights get automatically turned off when the set time is up for the day. Another point to make note of is to make sure you don’t put a very strong lighting source or direct sunlight as this can be another cause for algae to crop up in your aquarium.

2. Overfeeding Fish

As much as you love your fish ensure that you’re feeding just the amount that is required by them and not more than that. Fish food contains a high amount of nitrates and phosphates among other vital nutrients which are required for the growth and survival of the green algae.

Control your fish feed

Control your fish feed

By overfeeding your fish you’ll have a lot of remains that settle down in the tank. This food will slowly start letting out nitrates and phosphates into the water.

A combination of these nutrients along with light can lead to green algae popping up in your aquarium.

3. Unfiltered Water

Tap water or any other source of water that is not filtered has a lot of nutrients in them. Just like we humans require nutrients to perform day-to-day body functions plants require them too and thus these nutrients are the key to the survival of green algae.

Without these nutrients the green algae will not be able to function normally, starve and eventually die off. So make you use filtered water in your aquarium from now on.

4. Uncontrolled pH Levels

If the pH levels of the water isn’t kept in check then green algae can get comfortable in the environment and begin to grow and spread. The ideal pH level for water in saltwater aquariums is 7.6 to 8.4. Anything above the prescribed limit can lead to an imbalance in the ecosystem.

5. High Phosphate And Nitrate Levels

High phosphate and nitrate levels can be found in aquariums which can come from various sources.

Some of the sources we have discussed previously include unfiltered water and fish food, while some other sources include sea salt mixes and activated carbon among many of the other things you use to maintain your aquarium.

Ways To Identify Green Algae

Green algae is also known as hair algae because of its short and thin hair like structure that grows in a tightly packed manner.

Super-nasty Green Algae

Super-nasty Green Algae

Initially the hair like structure is short but over a period of time the length of the “hair” increases. Green algae comes in various shades of green right from pale green, light green to darker versions of green.

They can spread pretty quickly around the tank if it’s not controlled when spotted initially, so keep your eyes open for any green algae.

Ways To Control Green Algae

Now that we have a good idea as to what causes green algae to grow in our aquariums, let us take a good look at what can do to prevent and control this algae.

1. Be Generous With The Number Of Plants You Put In Your Tank

Fish often give off nutrients that plants absorb, but when there’s a lack of plants in the water algae starts forming and then they begin to reproduce rapidly.

Besides fish, other elements that are a part of your tank such as sea salt mixes and food for your fish can lead to excessive nutrient build up in the aquarium which can lead to green algae growth.

Having a lot of plants in your tank will starve the algae and eventually get rid of any algae that’s there in your tank. This is a great natural and long term method of keeping your saltwater aquarium clean.

On the flip side though, if the algae still manages to enter the aquarium and begins to spread it will begin to starve the plants because of how quickly they absorb the nutrients.

2. Control The Lighting

Too much or too little light can be disastrous for any fish hobbyist. It can be quite tricky to get the photoperiod spot on.

Too much light and algae can take advantage of that and wreak havoc in your aquarium, while too little light can limit the growth and requirements of other organisms in the aquarium.

3. Use A Protein Skimmer

Hobbyists swear by protein skimmers and many of them consider it the most important piece of equipment. Protein skimmers are often ignored by amateur hobbyists who tend to think it’s a waste of money.

They don’t recognize the importance of the role protein skimmers play. Protein skimmers work 24×7 to eliminate any excess nutrients that might have built up over a period of time in the tank.

Make sure that you buy a protein skimmer that’s large enough for your tank as it should have the capacity to filter the water that’s in your tank. Since it’s continuously cleaning up your tank, there’s lesser maintenance involved on your end. By eliminating excess nutrients, you’re getting rid of that nasty green algae!

4. Change Water Frequently

If you change the water in your tank frequently the chances of nutrient buildup in the water are much lesser.

Change about 25% of the water in your tank every fortnight and from there on experiment with the frequency of water changes as well as the quantity until you get the perfect range that works for you since every tank is different.

5. Use Filtered Water

Changing the water frequently might not be enough if the new water you’re putting is unfiltered and already comes with nutrients in it.

As you might know, tap water consists of high levels of nutrients and minerals which can lead to the growth of algae in the aquarium.

Regularly replacing the water with clean and filtered water can limit the chances of growth of algae and be one less source of nutrients in your tank.

6. Keep An Eye On The Ingredients In The Mixes

As a part of the routine to keep our tanks clean we often tend to use many chemicals in order to ensure that the aquarium’s ecosystem is functioning perfectly.

What we tend to overlook while doing this is the ingredients that come in these packs. Certain elements must be avoided at all costs if you want to keep green algae at bay such as iron, phosphates and nitrates.

These elements in particular lead to the growth of green algae in the water.

7. Phosphate/Nitrate Testing Kits

As a part of your algae tackling arsenal, use phosphate and nitrate testing kits to test phosphate and nitrate levels work as a great addition.

Having a master test kit is always handy

Having a master test kit is always handy

You might not know what’s causing the green algae to grow in the aquarium until you actually test the water to check for excess nutrient buildup. Checking on the levels of phosphates and nitrates will help you isolate the cause of the problem.

If the nitrate and phosphate levels are perfect then you might need to work around with your lighting or it could be that the algae is absorbing the nutrients too quickly thereby leaving minimal traces of nutrients in the water.

8. Add Mangroves To The Tank

Mangroves serve as a great addition to the tank as they not only offer a different aspect in terms of biodiversity but they also do a great job in absorbing phosphates from the tank.

The roots of the mangroves absorb phosphates present in your saltwater aquarium. Mangroves are a great natural way of getting rid of excessive nutrients in your tank and it doesn’t require regular maintenance nor is it too expensive.

9. Add Macroalgae To The System

Not all algae are bad algae; certain types of algae can be very beneficial to the overall health of the system.

Macroalgae fight for the same nutrients that green algae require and therefore if you have enough macroalgae, you’ll be able starve the green algae so that it disappears from your aquarium. They will absorb the excess nutrients and will also serve as food for many fish, thereby serving two purposes.

Share The Knowledge

You (un)officially have a Ph.D in green algae now! Use this newly acquired knowledge in green algae to help keep your tank clean and healthy. Do let us know in the comments section below what helped you rat out that nasty algae from your tank.

If you’d like to hear from us on stuff like this, please signup to our newsletter!

About Dennis Hanson

Dennis is an experienced aquarist with many years of knowledge and experience in keeping successful tanks. He also has no relations to the pop group Hanson.

2 thoughts on “Saltwater Algae Control: Green Algae

  1. Pingback: 7 Best Freshwater Aquarium Algae Eaters | Home Aquaria

  2. Reply Tim Sep 27,2015 2:47 pm

    3500 gal aquarium with algae problem. Know of any herbicide that can be used in an all fish, saltwater system. I successfully use Reward in my large outdoor ponds without fish harm but can’t seem to find out if it will be ok for saltwater

Leave a Reply