Aquariums around the world display beautiful marine life. It makes it easier for people who are not able to scuba dive enjoy the vivid beauty of the sea.

Likewise, aquariums are fun for both adults and children; however, if we cannot see what is on display, then where’s the fun in that? If your reef tank gets barraged with excessive Red Slime Algae, then you are in a pickle.

The most concerning issue is that the reason and source of this algae are not one but many. Therefore, we bring you this guide on Red Slime Algae in reef tank: causes and solutions so that you are on-guard when the time comes.

how to get rid of red slime algae

Red Slime Algae: A beginner-friendly definition

Actually, Red Slime Algae is not an alga at all. More specifically, it is a type of bacteria that forms a thick layer across the tank. Technically, it is known as a cyanobacterium that is considered to be a link between bacteria and algae.

This type of bacteria starts forming in small patches at first, then starts to spread outwards at a quick rate until the whole tank is engulfed in it.

It can appear in both saltwater and freshwater. Despite its whereabouts, its characteristics remain the same; it grows fast and spreads relentlessly.

What Are the Causes?

Most often, red slime algae are problematic in saltwater reef tanks. Its faster growth rate can become dangerous for marine life inside the tank, also a nuisance for you to clean later on.

First, you need to know why you have these algae in your tank.


Lack of maintenance often leads to tons of problems in a reef tank. If you fail to maintain the state of the tank, then algae would not be the only problem.

A common maintenance problem is slacking off when it comes to water changes, which then cause nutrients to build up, and accelerate algae growth. However, it is not this one factor; lighting fixtures is another as well.

1. Improper Lighting

In marine aquariums, this is the most common cause of red slime algae.

Most of the algae, especially the red slime kind thrive between 640-680 nanometres (nm).

However, most corals have a lighting requirement of 400-700 in the wavelength range. Thus, it creates a problem in handling the state of your tank.

Besides, bulbs with below 10,000K cause the growth of algae. With the age and use of bulbs, they lose their initial intensity.

As a result, more algae form if the bulbs are not changed when it’s dull.

2. Excess Nutrients

There can be many reasons for excess nutrients, and these come from a variety of sources, for instance, dead fish, lack of water changes, or badly cured live rock.

This is a very usual thing that can happen to anyone, even if you are a vigilant reef keeper.

Since this type of algae needs excess nutrients to survive in tanks, you need to know how to eliminate such nutrients that kill bacteria at the source.

Nutrients such as Nitrates (NO3) and Phosphates (PO4) are majorly involved in creating a habitat for red slime algae.

Phosphates establish itself into the aquariums through the use of unfiltered tap water.

Similarly, many aquarium products with a high concentration of PO4 such as KH buffers, foods, sea salt mixes, and many more create a friendly environment for algae.

Besides, the long-term use of Kalkwasser in reef tanks creates precipitation of phosphates, which then settle on rock and substrate as compounds.

Moreover, excess DOCs also increase nitrate problems in the aquarium. Though nitrates are established in the same manner as phosphate, there are means of producing it naturally as it is the final by-product in the nitrogen cycling process. It can occur due to a lack of proper maintenance or a new live rock in the tank as the curing process adds more nutrients.

3. Carbon Dioxide (CO2)

If there is low water flow throughout the tank, then it can produce carbon dioxide, which is not suitable for the tank’s condition. As algae consume CO2, production of it from less water movement accelerates the growth of algae.

What are the Solutions for Eliminating?

As soon as you pinpoint the cause of an algae outbreak, you are ready to fight.

Here, we listed some of the solutions for the common causes of your recurring algae in the reef tank. It’s time to get of those slimy bacteria.

1. Use Proper Lighting

First of all, you need to cut down any on your old, rusty lighting for the reef tank and have proper ones for the betterment of the tank.

  • Make sure to use the bulbs appropriate for aquarium only, and the cumulative wattage should be precisely set to your tank’s requirements. Any other bulb causes outbreaks of algae.
  • Keep the lights running for an average work hour (8 or maybe 9). Do not run the lights for more than your tank need as too much light causes explosive growth of cyanobacteria.
  • Make sure to a wide range of bulbs so that it increases the intensity and the spectral specialties of the lighting fixture should receive due optimization.
  • However, if you do not have corals inside the tank for some reason, then make a blackout for 3-4 days. If you keep the lights off for an extended time, then you can eliminate red slime algae at once.

2. Remove Any Nitrate Factories

Recent discoveries prove that bio balls and wet/dry filters produce a mass quantity of nitrates.

As mentioned before, algae feed off these nitrates.

  • Rinse these filters regularly to avoid excess nitrates production.
  • Also, clean these bio balls periodically.

3. Get A Phosphate Reactor

Phosphate also feeds algae and maximizes their population.

4. Add A Protein Skimmer

In saltwater aquariums, there is the presence of algae because of excess dissolved organics.

Hence, you need a protein skimmer that removes such organic compounds before they can harm your marine world.

  • For a sparkling clean tank, use a protein skimmer, which also removes organic compounds.

5. Cure Live Rock Properly

If your live rocks are improperly cured, it can introduce dozens of decaying materials into your reef tank. This type of organic material causes a spike in nitrates and phosphates.

  • Take time to make sure the rocks are cured when you are placing a live rock in your tank.
  • Check after adding the rocks into your water as well.

6. Increase Flow of Water

Red slime algae thrive when the water flow is weak. There are several devices available, depending on the size of the reef tank.

7. Keep Up with Regular Maintenance

For such a thing in your house, you need to maintain proper care at all times. You cannot slack off in the regular maintenance of reef tanks.

  • Regular cleaning of the substrate is an absolute must
  • Do not keep unnecessarily feeding your fishes and plants
  • Rinse or rejuvenate filter flosses, sponges, bio wheels, regularly
  • Consistently change the water albeit partially

Additional Tips

  • Beware of the nitrate or phosphate elements in everyday aquarium products.
  • Aquarium friendly substrate sifting devices, algae-consuming shrimps, crabs, or fishes can be of immense help.
  • Avoid adding new animals if your tank is going through a cycle.
  • Do not change filtering materials until the cycling procedure has come to an end.
  • For weakly attached algae, you can use light siphoning to remove it or just simply peel it off.
  • You can opt for a turkey blaster or nets when dealing with huge floating pieces.

Final Notes

Red Slime Algae is extremely hard to eliminate. It can be from a variety of sources that require different solutions.

It’s like your tower getting attacked from all fronts. However, you will have all the cavalry you need if you follow our instructions to the teeth.

Through this guide of Red Slime Algae: Causes and Solutions, you should be able to take better care of your reef tank.

Just make sure to keep a healthy fish tank, and all will be well.

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