The battle for pristine water quality in your saltwater aquarium is really never ending…


What if I told you there was a really awesome secret weapon out there that is naturally occurring and will suck a huge amount of pollutants out of your water and look really nice at the same time? And no, it’s not live rock…

Sounds too good to be true right?

Before I let you in on what the answer is I want share with you my brand new mentoring program: the Saltwater Aquarium Advice Academy

I created this program because most people who’ve invested in this hobby are extremely unlikely to succeed at the saltwater aquarium keeping, in fact 90% of people fail at saltwater aquarium keeping within 24 months, the most common reason for failure is not being able to create a consistent, pristine water quality environment necessary for marine life. My training program provide the tools I use to succeed.

Saltwater Aquarium MacroAlgae

Can you see the secret weapon? Just one of the many benefits you will get with my mentoring program…


The saltwater “secret weapon” I am talking about today will give your tank these benefits:

  • Enhance the look of your tank,
  • Provide food and shelter for your marine pets
  • Outcompete pest algae species
  • Oxygenate your tanks water
  • Improve your water quality by removing phosphates, silicates and nitrates…


The secret weapon or insiders tip is the strategic use of marine macro-algae; also known as saltwater plants!


saltwater aquarium tips

Image from my “Creating The Perfect Tank Environment” e-class. Having detritus munching inverts and macroalgae is a great clean team


There are 2 types of marine plants that commonly occur in saltwater aquariums

1. The (mostly) good species; these are the macroalgae (meaning “big” celled), the marine plants like Caulerpa and Halimeda and encrusting forms; the coralline algae.

These are desirable species because they look natural, grow predictably, oxygenate the water, suck out nutrients and are healthy snacks for our pets.

However there are one or two invasive macro-algae species you would not want in your tank, so research your prospective species well.

Most macroalgae species come from the groups Chlorophyta (green algae), the popular coralline species from the group Rhodophyta (red algae) and Phaeophyta (brown algae).


2. The (mostly) bad species: the micro-algae (meaning “small” celled) these are single-celled algae species, which converge in our aquariums en-masse and have a phenomenal reproductive capacity. Its these micro-algae’s out-of-control growth that cause blooms that can threaten our entire marine tanks. The most notorious of the micro-algae’s are:

  • Blue/green algae (Cyanobacteria): Blue-green slime algae is responsible for a lot of saltwater aquarium mayhem, these single-celled organisms are more related to bacteria than algae. In colour this algae ranges from red all the way through to bluish-black and can be seen as slime, hair-like threads or a smear of evil looking film. Blue-green algae covers everything in its path and is very tolerant of water parameters but does best in high phosphate, well-lit environments.
  • Hair algae: Also known as filamentous green algae and officially as Derbesia species. This is one of the most annoying algae’s and is very common in saltwater aquariums. Its growth as im sure you can guess resembles clumps of feathery hair that are green.
  • Bryopsis: Bryopsis is a green macro-algae and also goes by the lovely name of Sea Fern, but this stuff is anything but lovely in your aquarium. It grows very fast and its green-brown feathery mass can take over your aquarium in a couple of days! Bryopsis is often introduced on live rock and is commonly mistaken for Hair algae or Caulerpa.
saltwater aquarium improving water quality

Want some 1-on-1 help to create the best tank possible and fast-track your success? I can help.


So, it’s micro-algae species that cause the huge majority of pest algae problems in marine aquariums.

They cause problems by covering every object in the tank (and the glass) including corals and other invertebrates that they can suffocate, cause infection and block out their light all of which can cause damage and even death.

Some algae are even toxic if eaten.

Pest algae outbreaks also suck out massive amounts of oxygen from the water at night, clog up filters, destroy water quality with their decaying biomass and generally look nasty preventing us from seeing our lovely fish and corals!

saltwater aquarium tips

Here is tank stocked exclusively with macro-algae species. Pretty huh? (photo credit: thesaltybox.com)


Macroalgae on the other hand is very helpful and will do these 5 fantastic things for your tank:

  • Out competing the pest algae species by using up all available nutrients in the water faster and more effectively. This means pest algae will not have a chance to thrive.
  • Provides a great supplementary food source to herbivores and omnivores alike. Occasional browsing will also encourage the algae to grow well. Tangs, Angelfish, Blennies, crabs and snails all benefit from algae growing in the tank. A diet rich in algae is said to dramatically reduce the incidence of head and lateral line erosion disease (HLLE) in Tangs and Angelfish
  • Acting as a water filter sucking organic nutrients out of the water such as nitrates, phosphates and silicates that come from the breakdown of food and waste. Corals especially are very sensitive to these compounds. Algae also helps to absorb heavy metals and any toxins released by marine organisms
  • Add much needed oxygenation to the water column. Marine plants take in carbon dioxide and put out oxygen, you can never have enough oxygen in a saltwater environment
  • Gives your aquarium a more natural, authentic look and provides habitats for invertebrates and hiding places for invertebrates and marine fish


Creating an ideal habitat for macroalgae

Macroalgae are very easy to care for and only really require fairly clean water and the same bright (high) lighting that photosynthetic corals and anemone require, so are perfect for reef tanks.

They need about 8 hours per day of light to thrive. Interestingly pest micro-algae’s do better in dim lighting.

They will not need any supplementary feeding, as they will mop up excess nutrients in the water. Coralline (red) algae also need a calcium supplement to grow best.

If your marine plants are growing too much (this is usually a pretty slow process for macroalgae) you can simply trim and prune them as you would land plants.

Personally I like to keep the base of my aquariums free from substrate (much easier to keep clean this way ;) and encourage the growth of encrusting macro-algae’s across the base and strategically plant clumps of Halimedia and Caulerpa on the live rock where it looks really pretty.


Types of macroalgae:

1. Caulerpa species: This rapid-growing and popular macroalgae comes from the phylum Chlorophyta which are the green macroalgae’s. There are more than 100 different species of Caulerpa some forms growing tall and others growing as mats. The “feather” and “grape” varieties named after the forms of their leaves are the most popular with aquarists. Caulerpa is a favourite snack for marine herbivores and is very good for filling in empty spaces in marine tanks. Caulerpa plants are attached to each other by runners or rhizomes, which they use for anchoring themselves to the rock.

2. Halimeda: This Hawaiian macroalgae also of the phylum Chlorophyta incorporates calcium into its plate shaped leaves so is not eaten by herbivores. It is a slow grower and forms baseball sized, circular clumps. It is an attractive and hardy macroalgae to have in your saltwater aquarium.

3. Coralline algae: The bright red/pink/white/purple encrusting varieties of coralline algae (phylum Rhodophyta) are a huge favourite of reef tank owners. They always come introduced on live rock but can also spread onto glass bottoms, they can also be propagated by taking scrapings or existing colonies to new areas. Also being calcium absorbing they need decent levels of calcium (400 – 440 mg/mL) like corals. Also like corals they don’t tolerate much phosphates or nitrates and also need magnesium, which will encourage them to thrive. Coralline algae is vital to holding together coral reefs in the wild and is said to produce chemicals that promote the growth of invertebrates, they also keep pest algae away and provide a magnesium source for the tank.

4. Turtle grass: Also known as Maidens hair Chlorodesmis is also from the phylum Chlorophyta and resembles fine blades of grass that look like tufts of bright green hair. In my opinion this is one of the most attractive macroalgae’s because of its colour and form. It wont be snacked on because it contains a deterrent in its leaves. It needs moderate to strong water current and lighting.

Aquarium macroalgae

Photo from page 99 of “Creating the Perfect tank Environment”: Turtle grass is rather attractive and fish love it


A GOOD IDEA: using macroalgae as a filter that scrubs the water

One of the most effective uses for macroalgae involves growing it in a sump or refugium below or to the side of the main tank.

This algae “scrubber” once established will massively filter phosphates, nitrates, some heavy metals and toxins from your water and add large amounts of oxygen.

As well as the obvious benefits an algae filter means pest algae will not be able to grow in your display tank. All you need is a continuous flow of tank water in and out of your algae chamber and about 18-24 hours of light daily for maximum effect, the reason for near continuous light is so that release of carbon dioxide in the dark periods is kept to a minimum, which will decrease pH.

You can also keep live rock, live sand in your refugium/sump and raise amphipods and copepods to feed your marine life at the same time as grow algae. Algae in the scrubber needs to be regularly pruned and excessive growth removed.

The best alga to use for this task is Chaetomorpha or spaghetti algae which has become very popular with reefers in the last few years. This algae grows in dense balls resembling a ball of green fishing line. ‘Pods eat this algae as well. Chaeto grows under regular fluorescent lights.


Hopefully this blog post will have taught you the relatively little known massive benefits of macroalgae and the huge advantages it can offer your marine system.

If you would like more insiders tips on having more success with your saltwater aquarium life support system, check out my new mentoring program The Saltwater Aquarium Advice Academy and try out your 1st month for just $7!