Learn How To Control And Prevent Algae For Good

If you find yourself as one of those unfortunate souls who is constantly fighting algae outbreaks stay tuned here because we are giving you the tools to stop that forever. You can expect to learn why algae happens, how to clear it up and prevent it from coming back for good.

New tanks are finicky. Some of you may have followed all of the common advice for avoiding algae problems yet still find yourself dealing with an algae farm. The rest of you, likely ignored some of that advice and decided to learn the hard way. Regardless, you are all here for the same reason and that is to stop algae from ruining this hobby for you.

Side by side algae rock vs clean rock

Algae is one of those things where an ounce of prevention is worth a pound...no 100 pounds of cure!

It is also important to understand that once algae gets a stronghold in your tank, it will take many months to clear it up. It is not hard, it simply takes time and persistence. We organized our algae eradication approach into a series of steps that get progressively more aggressive and surely one of them will work for you.

Nitrate rock

#1 - High Nutrients and Bright Lights

Elevated nitrate and phosphate levels combined with those high output lights your corals need are what often lead to algae issues in new tanks. It is pretty rare, however, that a reefer can eliminate algae from their system just by lowering nitrate and phosphate alone.

Important Note: If your water tests are showing low levels of nitrate and phosphate yet algae persists, the nutrients are locked up in the algae which has already used it to grow. Algae grows fast, in fact it is one of the fastest growing photosynthetic organisms on the planet.

While lowering the phosphate and nitrate levels may not eradicate algae from your system, it is an important step to making sure it doesn't come back. So related to that consider your feeding habits and approach to filtration for the future. If you see nitrate or phosphate rising, stop feeding so much, it is that simple. If you can’t help it then boost your filtration with a better skimmer, add a refugium or increase the water change frequency until the levels stop rising.

Manual algae removal

#2 - Manual Removal

Whenever possible, physically remove the algae from your tank. DO NOT scrub your rocks and let the algae float around and spread throughout your tank and filtration.

Algae removal with a siphon tube

Use a siphon tube and your thumb to pinch off the tufts of algae and suck them out of your tank. Doing this will not only get rid of the algae but also those locked up phosphate and nitrates it contains. Just like harvesting macroalgae from your refugium, only this time it is nuisance algae from your display tank.

Do this weekly or as often as possible; get the algae out of your tank as soon as you see it. After a few weeks or more, you should see it start to slow down so long as nutrient levels are under control.

Yellow Tang

#3 - Utilitarian Fish: The Tang Gang

Turn to the Tang Gang or fish that eat algae for a living. A few of these herbivorous fish are the most effective component of a clean up crew, end of story. When established, they can eliminate all signs of algae in a matter of days to weeks.

Some feed more aggressively than others or like different varieties, that is why multiple types of algae eaters are the best practice. Even if you have small tanks like our 40-gallon tanks, there are Tang options. Just understand they will outgrow the tank within a few years or less. Most reefers will upgrade tanks by this time but even if you don’t upgrade to a larger tank, finding those large fish new homes is a legit option.

Long Spine Sea Urchin

Many local fish stores will accept a trade in as well, larger fish sell for more money so it would only make sense. This is also just another reason to establish a friendly relationship with your local fish store.

If you just can’t add multiple species of Tangs, there are other livestock options. Snails and crabs are great, Mexican Turbo Snails and Sea Urchins are the most effective but rarely will these “clean up crew” animals be a complete solution. A crew of different tangs, however, can easily eradicate algae completely.

Heterotrophic Bacteria

#4 - Heterotrophic Bacteria

If the multi-stage attack on algae is just not working, then it may be time for a more aggressive approach. Aggressive means there are sometimes unintended consequences but these are generally considered safe.

Bacteria, specifically Heterotrophic Bacteria that need to consume food, will eat algae as well as decaying organic matter.


Vibrant and Brightwell Aquatics MicroBacter Clean are both very effective bacterial additives for this purpose. Vibrant is a bit more aggressive and the only product we have witnessed to completely eradicate Bubble Algae from a reef tank. These bacteria do not reproduce in saltwater so repeated doses are required. Don’t be impatient while dosing the bacteria, if you are not seeing results right away, just keep at it.

If you overdose the bacteria in an attempt to make it work faster, new pests such as other algae or bacterial slimes can take its place. Moral of story is plan for at least 2 months of dosing and follow the manufacturer recommendations for our tank size.

Reef Flux

#5 - Fluconazole

Fluconazole, the main ingredient of Reef Flux, is sold to treat fungal infections in fish but reefers found that it can also completely eradicate algae from the tank by inhibiting some important metabolic functions. Most notably, reefers use it on one of the most difficult to beat algae species, Bryopsis. At one point in time Bryopsis was nearly impossible to eradicate in home aquariums.

There is always some risk to aggressive solutions. While everyone will have a different experience, the only effect we can report is a reduced uptake of calcium and alkalinity. This leads us to believe some stress on the system is happening, just not very obvious at a glance. We use it here at BRS quite often to treat Bryopsis.

Peroxide Coral Dip

#6 - Hydrogen Peroxide

If all else fails, drain the tank down and just kill the patches of algae with direct application of Hydrogen Peroxide. Yes, the same stuff used to clean up a scraped knee or small cut. You can get it at a drugstore in a spray bottle and just spray it right on the algae, let it sit for a few minutes before filling the tank back up.

Many corals tolerate the peroxide, even directly on the tissue. Some reefers use peroxide as a coral dip to remove algae from frags. At the same time, do your best to avoid spraying your coral.

Spraying hydrogen peroxide to kill algae

Peroxide will not kill the roots of the algae so it can and will grow back if left alone. It will kill the algae way back to a point at which it will be much easier to eradicate with the less aggressive solutions.

With 100% certainty, this 6 stage escalation will eradicate an algae problem in your tank. Ideally, one of the less aggressive first steps will work. None the less you now have a plan and paired with good practices can effectively keep algae out of your tank.


What’s Next

Next to algae, that red slimy stuff that never seems to go away called cyanobacteria is one of the most frustrating ailments new reefers face. Luckily cyano is easy to control if you just have the tools and knowledge to get through it. Up next, we teach you all about cyanobacteria, how to prevent it and finally how to get rid of it.

5 Minute Saltwater Aquarium Guide Episode #26

Looking for a different topic or have questions? You can binge the entire 5 Minute Saltwater Aquarium Guide playlist right here on our website. We also invite you to join the #askBRStv Facebook Group which is a free resource for you to ask questions, get advice, interact with other hobbyists and get your daily reef aquarium fix.

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