In my time working at a local fish store, I have come to realize that hobbyists that have been keeping saltwater tanks for years often run into similar problems as new hobbyists. But, most of newcomers’ algae problems are simply due to their tank naturally cycling, and they resolve themselves within a month or two without any interference needed. Diatoms, hair algae, and cyanobacteria are all things that nearly every new tank will see, and beginners simply wait it out, as tank maturation and normal routine maintenance will cure these problems. I have realized that it is the keepers who have had their tank for a few years that are the ones now running into issues with algae overwhelming their systems, coming in to ask how to remove red algae from saltwater tanks or how to cure hair algae. Since cyanobacteria can be one of the most difficult problems to correct, we will focus on that in this article.

Identifying Cyanobacteria

Even though most of us can easily identify cyanobacteria, there are some more uncommon phenotypes that have confused hobbyists. Typical cyano is red or purple in color and starts as thin patches in the sand bed and rocks. It quickly grows, and the patch thickens into a slimy, velvet like blanket that can cover everything in the tank. It can be easily removed by using a turkey baster, powerhead, or hands and peels off in sheets or clumps. But, not all cyanobacteria are the reddish-purple color. It may also be black, green, bluish green, orange, brown, or bright red. Sometimes, the blanket of bacteria can also grow hair-like strands that easily break apart.

What Causes It?

There are numerous aspects to your tank and maintenance that can encourage cycanobacteria growth. Bad lights, stagnant water, tap water or RODI with more than 0 TDS, skipping water changes, old live rock, overfeeding, long photoperiods, low pH, lower quality salt, low oxygen levels, and lack of protein skimming are all major contributors. Most of these are easy remedies. Be sure your skimmer is working efficiently, remember to check the TDS meter on your RODI unit (or invest in a good system if you haven’t already), use kalkwasser in your top off water, utilize powerheads, and only feed what your fish can eat within a couple minutes. We will go into more detail about lighting and water quality later on.  I will also add that when I had cyanobacteria problems in my tank, simply changing from my typical salt (a very popular, low cost salt) to a higher quality, purer salt with fewer anticaking agents solved my problems in and of itself. While salt mixes causing algae problems is highly debated, I have had many, many customers try the same experiment with a new salt and all but one saw drastic improvement. Most were able to completely cure their algae problems by simply switching from the salt we all originally used. Again, this a very highly debated topic, but my personal experience leads me to believe that this is a good first step if your routine maintenance is already up to par.
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How to Remove Red Algae from Saltwater Tanks

If your red slime algae hasn’t gone away by addressing the above, there is a strong possibility that nutrients or lighting is the culprit. Old or improper bulbs or LEDs set to the wrong spectrum, or burning out, all encourage algae growth. T5HO and metal halide bulbs should be changed regularly, about every 8-11 months. LEDs should be monitored and replaced when diodes start to dim or shift colors. No matter what light you use, be sure to stay in the 12,000-20,000 Kelvin range, as lower Kelvins also encourage cyano blooms. Finally, limit your photoperiod to 8-10 hours a day, as this is all a reef tank actually needs.

After lighting problems, nutrients are the other major cause of cyanobacteria problems. While tests may show little to no phosphates and nitrates, that is simply due to the algae consuming it as fast as it is produced, and your tank does indeed have excess nutrients. The biggest reason cyano is typically a problem for intermediate hobbyists is due to the fact that we have a tendency to get too comfortable, and slack in the tank maintenance department. We are more likely to skip water changes, put off replacing carbon and GFO, stop checking our TDS meters, etc. To get rid of cyanobacteria, make sure you are doing water changes at least monthly, you have fresh carbon and GFO, and your RODI water has 0 TDS. If you typically use don’t use RODI water, or don’t run chemical filtration, this is a good time to start as algae outbreaks are a sign of your tank needing that little bit of extra help.

If you try all of the above, and you still cannot find the source of your excess nutrients, consider your live rock. In heavily stocked tanks, it is not uncommon for live rock to completely “fill up” with nutrients. Once the rock has taken up as much nitrate and phosphate as it can, it will leech back into your system and create the perfect breeding ground for algae and cyano. This typically takes 5 to 10 years. If you are at this point, it may be time to cook your live rock. Check out our article on how to do this if you haven’t done this before!

Other Methods

If you try to eliminate cyanobacteria by simply vacuuming it out of your tank or scrubbing it off of the rocks without addressing the underlying issue, expect it to quickly return. Some people will use products claiming to be a “cyanobacteria or red slime remover.” While these can definitely be used to buy you time to solve the underlying problems, it will not cure cyanobacteria if it is the only thing you do. It will simply kill the bacteria now but do nothing to prevent future blooms. So, while it can be used to quickly kill cyano and keep it from killing your corals, it is not a cure-all. Also, Court Jester Gobies have been known to pick at cyanobacteria, helping with removal!

Now, you may be wondering how to remove red algae from a saltwater tank naturally. Most people will quickly jump to buying clean up crew members that are supposed to eat red slime. Again, this is a good option, but the actual issue of what is causing cyanobacteria to grow in your tank must also be addressed. Trochus and Cerith snails are the best inverts to purchase to eat it, most other crabs and snails will not touch this bacteria. But, these two will quickly clean a light bloom and keep your tank looking clean while you work to find the problem. Cyanobacteria is unsightly, dangerous to corals, and difficult to get rid of. By keeping up on routine tank maintenance, you can prevent an outbreak and keep your tank looking beautiful. After all, prevention is the best remedy!
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