How to Control Algae in a Reef

Whether you are new to the reef hobby, or you’ve been keeping reef tanks for years, one thing that will always be on your to do list will be some form of algae control. Whether it be hair algae, Valonia (bubble algae), Bryopsis (fern algae), Ulva (sea lettuce), or the ultra-pervasive cyanobacteria (slime algae) there is generally a “check list” you can work your way through in order to cut down and ultimately defeat your algae problem.
All the algae on the previous list needs two things in order to survive: light and nutrients. We will always have both of those things in our reef tanks, so it is our job as hobbyists to keep them in proper balance in order to prevent an uptake of algae in our tanks. When it comes to lighting, 8-10 hours is usually all our corals will require to have adequate time for photosynthesis. Of course, every type of light for a reef aquarium will have different levels of controllability, and some may offer the ability to customize your light spectrum. I won’t go into extraneous detail on reef lighting in this blog, but I will say that when battling algae in your tank, lowering the intensity of your green, red, and white spectrums can aid in your quest to eradicate it. Don’t forget, sunlight counts! If any part of your tank is getting direct or indirect sunlight, even if it is only for a few hours per day, algae will utilize this light source just like it would any other! Light intensity and duration issues are generally the easier part of the equation to address.
When it comes to nutrient levels, it can be difficult to achieve what many sources will tell you are “perfect” reef conditions, i.e. nitrates at less than 5 ppm, and phosphates at .03 ppm. Generally, I have found that this can vary from tank to tank, but I usually go with a more forgiving nitrate level of less than 20 ppm, and phosphates between .03-.1. Monitoring these levels is extremely important and you will want a good test kit at your disposal for regular testing. This is not to say that you will not have algae even at “perfect” nutrient levels, but in most cases tanks that fall within these ranges are not having significant issues. Luckily there are many things than can be done and many products that can be utilized to control your nutrient levels.
Chemical filter media can be effective in controlling phosphate levels. Phosguard is great product for general use in a reef tank, I usually recommend it as something that is used proactively for most new reefs. Chemipure Elite is another product that fills this role quite well. When phosphates are significantly higher I would recommend the use of a fluidized media reactor paired with a GFO media (granulated ferric oxide) like Rowaphos. I find this will work MUCH more quickly in problem situations when phosphates are significantly out of range, sometimes in a few days. For nitrates you can use Algone or a Nitrate Reducing Pad. Regular water changes are also important in lowering these levels when they are outside of normal ranges. Remember that one water change is rarely enough to make a significant impact in lowering nutrient levels.
Carbon dosing is a tactic commonly used by aquarists to stimulate natural bacteria in your aquarium in to doing your nutrient management for you. Red Sea's NOPOX can be used daily to begin dropping your levels in as soon as a few weeks. Dr. Tim's Biopellets can be added to a fluidized reactor as a form of continual, relatively hands-off form of carbon dosing.
Bacterial additives can be an ally of yours in the battle against many different types of algae, either by attacking the algae’s food source, or the algae itself. Products that I have used and found effective include Dr. Tim's Refresh, Waste Away, Waste Away GelSeachem's Pristine, Aqualife's Activate,  and Underwater Creation's Vibrant).
Unfortunately addressing your lighting and nutrient levels is only the beginning of the battle. Once the corrections have been made you should see a significant decrease in the growth rate of your algae, but usually the algae that HAS grown is still in the aquarium, staring you in the face. This is the time for physical removal by you, and the addition of algae grazers into the aquarium. Clean Up Crew, Urchins, and Emerald Crabs can be great additions to reef tanks of almost any size for almost any type of algae. They will help consume the algae that is still clinging on stubbornly after you have hopefully deprived it of what it needs to grow. In larger tanks fish may be used to help you as well Algae Blenny, Foxfaces, and Tangs can be good additions if you have the required space to house them.
When all of this still isn’t enough to wipe out your algae problems, some more aggressive tactics can be employed as a last resort. I usually save it for last because although these products are “reef safe” they can temporarily irritate corals when in use. For “slime algae” or cyanobacteria Chemiclean and Red Slime Remover work great, and for hair algae/Bryopsis Flux RX is our go to. I like to start with half to two thirds the recommended dose as it is often enough to knock out the algae while sparing your more irritable corals. The only time I have seen these products fail to work properly is when the lighting levels or nutrient levels have not been addressed first, or when they are used improperly. Just remember to have enough saltwater on hand to perform one or multiple water changes when utilizing these additives.
Remember that once you have got your algae under control, it is important not to get complacent. Keep changing your chemical media, regularly repacking your media reactors, adding your bacterial additives, and most importantly performing regular water changes! Only 3 things in life are certain: death, taxes, and algae growing in your tank!

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