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How to Get Rid of Cyanobacteria in a Reef Tank
My favorite aspect of keeping a saltwater aquarium is being able to enjoy the beautiful aquascape I’ve spent so much time carefully designing and nurturing. Unfortunately, this can be disrupted by the appearance of red slime creeping over everything. This slime is called cyanobacteria and can be dangerous for soft corals.
Thankfully, cyanobacteria are pretty easy to get rid of. This article will take a look at how to get rid of cyanobacteria in a reef tank and how to make sure it stays away.
What is Cyanobacteria
Cyanobacteria are often referred to as red algae, but it’s not totally an algae, nor is it always red. Cyano actually has properties of both algae and bacteria. It’s photosynthetic but also feeds off of organic compounds like phosphates and nitrates.
Cyano most often appears as a red, slimy substance, but it can also be green, black, or purple. It’s actually considered one of the earliest forms of life on earth and plays an important role in the production of oxygen for our planet.
While it may be good for the world, cyano is not something you want in your tank. It’s a single-celled organism that is invisible to the naked eye but grows in large colonies that can eventually take over a tank if not stopped.
What Causes Cyanobacteria
When looking at how to get rid of cyanobacteria in a reef tank, it’s important to first know the causes. These can include:
- Low water flow
- Bad lighting
- High phosphate and nitrate levels
- Bad source water
- Infrequent water changes
- Bad filter maintenance
One of the leading causes of cyano blooms is high levels of phosphates and nitrates. This can happen if you are over-feeding your tank or not using proper feeding techniques. High nutrient levels can also be caused by not changing out your water enough or by not maintaining your filtration systems properly.
Another big cause of cyanobacteria growth is dead spots in the water. Low-flow or still water is a perfect place for cyano to grow, so you may find yourself struggling with this organism if you don’t have enough pumps to circulate your water, or if they’re not strong enough.
Bad lighting can also lead to cyano growth. This can especially be a problem if you are using T5 lighting systems or fluorescent bulbs. As these bulbs age, the spectrum of light they emit changes from ranges that promote coral growth to ranges that promote algae growth.
Finally, your source of water can be causing your cyanobacteria problems. You should never use tap water for your aquarium as it will bring with it all kinds of minerals and deposits, including phosphates and nitrates. Adding a dechlorination agent won’t be enough to remove excess nutrients which will contribute to cyano growth.
How to Get Rid of Cyanobacteria in a Reef Tank
Getting rid of Cyanobacteria (red slime) can be a challenge but if you follow the steps below you should be able to remove it successfully.
Water Changes
Frequent water changes will help keep phosphate and nitrate levels down which will make it harder for cyanobacteria to grow. Keep in mind that cyano will lock in phosphates and nitrates, so your levels may look normal even if there is an excess of these nutrients fueling cyano growth. This is why it’s important to change your water out on a regular schedule. Frequent small changes work best to deal with algae blooms, but less-frequent, large-volume changes will help as well.
Siphon and Scrubbing
Often, the best way to get rid of cyanobacteria is to physically remove it. This can be done with a siphon, though you may need to use a toothbrush to carefully dislodge cyano from rocks and other surfaces first before sucking it out.
Chemical Treatments
Chemical additives are also a good way to kill off cyano growth, especially if you have a lot of it or it’s growing in places that are hard to reach.
Boyd Enterprises Chemi-Clean is my go-to chemical for algae removal. It works quickly, is safe for all tank inhabitants, helps balance enzyme levels, and doesn’t use algaecides or antibacterial agents. Just don’t use more than the recommended dose for your tank and turn off your protein skimmer for 48 hours while it’s working.
You may want to add an airstone during this time or redirect your current to increase surface agitation to make sure your oxygen levels don’t drop too low.
How To Keep Cyanobacteria From Coming Back
Now that you have removed the Cyanobacteria from your reef tank, let’s talk about how to keep it from coming back.
RO/DI Water
To avoid adding phosphates and nitrates to your tank, you should run your tap water through an RO/DI system. This stands for reverse-osmosis/deionization system, and you can easily set one up in your home to purify your tap water.
Better Lighting
Be sure to switch fluorescent lights out frequently, even before they start to dim. If you struggle with recurring cyanobacteria blooms, you may want to invest in LED lights and make sure they are set to the right spectrum to encourage your corals, and not algae, to grow.
Better Water Flow
To ensure you don’t have dead spots in your tank, you may need to either add more powerheads or find ones that will produce a stronger flow. You may also need to rearrange your rocks and corals to allow for better currents throughout the tank.
Adding Algae-Eating Creatures
Algae-eating creatures won’t fix a cyano bloom, but they are excellent at keeping tanks clean and preventing developing algae colonies from turning into full-blown problems. My favorite algae-eating creatures that love cyanobacteria include:
- Trochus Snails
- Cerith Snails
- Mexican Red Leg Hermit Crabs
Final Thoughts
Cyanobacteria is ugly, prolific, and potentially dangerous. Fortunately, the question of how to get rid of cyanobacteria in a reef tank is simply to implement frequent water changes, physically remove the cyano, and use chemical intervention if necessary.
Good filtration, lighting, currents, source water, and a few algae-eating critters will all go a long way to ensure your tank stays as clean as possible and large cyanobacteria blooms are a thing of the past.
