Pest algae outbreaks are a serious pain…


There is nothing worse than looking in your saltwater aquarium and seeing a hideous outbreak of pest algae completely coating your rock-work, or worse, your corals!

But this nasty outbreak could have been avoided…However it can be fixed and stopped from ever coming back. Want me to show you the best ways?

Before I let you in on what my solutions are, I want share with you my FREE “Saltwater Success Tools” ebook promotion – get some of my best saltwater scientist tips, trick and hacks to avoid making the top aquarium mistakes so many others make!

I wrote this free guide because around 90% of people fail at saltwater aquarium keeping within a year, the most common reason for failure is not being able to create a consistent, pristine environment necessary for thriving marine life.

pest algae

Common problems like pest algae outbreaks can be easily prevented, my ebook shows you how


How to stop pest algae thriving in your saltwater aquarium

Whether you are suffering from hair algae, bubble algae, Bryopsis, diatoms or blue/green algae (cyanobacteria) excessive algal growth is almost always caused by the same factors:

  • Too much nutrients in the water (mostly nitrates and phosphates, but also silicates)
  • Old/inappropriate lighting or natural sunlight hitting your tank
  • Poor water movement

Pest algae can be a real nightmare to get rid of, if you have an outbreak there are a number of steps you can take to get rid of it that work, either by themselves or in conjunction with each other.

These are the quick fix solutions below…


 Pest Algae quick fix solutions:

  •  An algae-grazing aquarium crew: An assortment of these helpful aquarium tank mates should be able to keep that algae under control: Sea urchins, Turbo and Astrea snails, some Tangs especially sail-fin Tangs, some Blennies especially the aptly name Lawnmower Blenny and crabs such as Emerald crabs. Do your research first and make sure they are suitable for your tank and existing pets.
  •  Algaecides: There are a number of good algae destroying products on the market (link to additives, algae stoppers) such as Kent marine tech M for Bryopsis outbreaks. Some can damage biological filters as they are antibiotics, herbicides and the like so once again research carefully.
  •  Scrapers and magnet cleaners: Good old manual labour goes a long way and of course is the most direct measure to deal with your problem. Many products are available for this purpose.
  • Reducing light: If you have a fish only tank, then you can have blackout periods of a few days to kill off the algae. Obviously if you have any photosynthetic species including live rock this will not be a good idea.
  •  UV Sterilizers: These are actually very good at destroying floating particles of algae (single celled micro-algae’s which are mostly our pest species), they are devices which radiate the water passing through them with Ultraviolet (UV) light killing organisms like algae, bacteria, parasites. Powerheads do the job of pumping water through the UV sterilizer.


micro-algae outbreak

A Scopas tang is a voracious algae eater, they are also peaceful and reef safe.


So, do you want a quick fix or a permanent fix?

These quick fix solutions all work fine, however I would advice you to look deeper, there is an underlying cause of your outbreak and if you want to get to the bottom of it, instead of praying the algae doesn’t come back again, you need to treat the cause not the symptoms.

Rule out the following underlying problems one by one, wait for results for each, this is showing you what is working and what isn’t, enabling you to ensure it doesn’t happen again, hopefully ever!


Underlying problem 1: Too much phosphate

Phosphate (PO4) is probably the most important element in the growth of plants (including algae). To find out whether this is your problem you will need a phosphate test kit (phosphate should be undetectable in a healthy tank) and also to pay closer attention to what is going into your water.

Phosphate can come from:

  • Overfeeding (fish foods contain phosphate), of particular importance here is the juice from frozen foods, defrost and get rid of it. You can test foods by mixing them up in a little water and reading after 20 or so minutes.
  • Tap water can contain phosphates, RO filtered water (link to RO filters) will get rid of phosphate, nitrate and other nutrients, heavy metals and so on
  • Aquarium additives can contain phosphates.
  • Activated carbon, some brands have phosphates, put some in water and test it!
  • Long-term use of Kalkwasser precipitates phosphates out of the water making them insoluble and so unavailable for algae. But in localised areas of the tank the pH can drop from built up debris, which actually releases the insoluble phosphate settled on the rocks in that area into the water! So rockwork should be wiped down from time to time.


aquarium pest algae outbreaks

Feeding lots of large fish too much can easily lead to excessive phosphate and nitrate levels which pest algae loves.


Underlying problem 2: Too much nitrate

 Nitrates are the other major chemical elements algae thrive on. Nitrate (NO3) is the resulting compound from from dissolved organic waste and accumulates in the water all the time unless removed. Get a test kit and check this out.

Ways to reduce nitrate are:

  •  More regular partial water changes go for a higher volume per week like 10% water replacement. You should be topping up evaporated water with pure water not tap water.
  •  Use RO/DI or some other form of purified water.
  •  Vacuum your gravel more often and make sure you get rid of settled detritus. A good glass and rockwork wiping now and again helps as well.
  •  Get a protein skimmer, these remove dissolved organics at the source (before they get converted to nitrate) they are VERY good at keeping the water pristine.
  •  Clean out or replace your filter media regularly, organic debris can easily build up in here adding to the nitrate levels in the water.
  •  Feed less, only feed as much food as your fish will eat in a few minutes, less is more!
  •  Purchase a nitrate reducing system (like a nitrate reductor) or some live rock (I can never have too much of this stuff!), which has anaerobic zones, which will convert nitrate into harmless Nitrogen gas.
  • Get some macro-algae species, they look cool, oxygenate the water and will effectively out compete the pest algae for light and nutrients. They can either be kept in the display tank or in a lit refugium. You can’t go wrong here!


getting rid of algae

Keeping macro-algae species helps out-compete pest algae which are usually micro-algae’s. My “Ultimate Secrets” ebook has more information about this technique.


Underlying problem 3: Too little water movement and too much CO2

 Too little water movement makes “dead” zones perfect for algal growth that like stagnant waters, if there isn’t enough water movement CO2 will probably be high and saturated oxygen levels will be down also.

 You don’t want so much water sloshing around that fish cant swim properly but good, vigorous multi-directional water movement helps stir up detritus (so it is picked up by the filter or skimmer), feeds corals their food, oxygenates the water (thus reducing CO2) and makes conditions generally unfavourable for pest algae. All this is achieved by a couple of simple powerheads strategically placed pointing at each other.

aquarium pest algae

Image from page 99 of “Success With Corals”: Once micro-algae starts growing over coral, the coral becomes starved of light and can easily die.


Underlying problem 4: Old lighting or too much natural light

You should always change your bulbs as per the manufacturers instructions; either once a year or every 6 months. As bulbs age their color spectrum changes and produces more and more light that algae like! Algae like less intense light over shorter time frames.

Natural light (sunlight) is obviously what causes algae to grow in nature, so you want as little as possible hitting your aquarium. Algae also like heat so if your aquarium is hotter than it should be this will favor algal growth.


pest algae fix

The only algae I want in my system is macro-algae for snacking, oxygenation and improving my water quality (photo credit; timuiuc)

 So, algae are actually beneficial to the saltwater aquarium environment when it can be groomed and trimmed and trusted to not over run the tank.

When you get an algal bloom it can be fixed immediately using the strategies above however this outbreak is caused by an underlying problem so if you don’t want to periodically be trying to reclaim your aquarium from these plants I recommend you get to the bottom of it!

If you would like more insiders tips on avoiding mistakes and enjoying more success with your saltwater system, check out my free “Saltwater Success Tools” eBook promotion