Today, I want to let you in on a great insiders tip to:

  1. enhance the look of your tank.
  2. provide food and shelter for your marine pets.
  3. outcompete pest algae species.
  4. oxygenate your tanks water.
  5. improve your water quality by removing phosphates, silicates and nitrates.

This tip is the strategic use of marine macro-algae; also known as saltwater plants and coralline algae!

Macro-algae (meaning big celled algae) species should not be confused with micro-algae (small celled algae) which are those common pest algae species such as  Cyanobacteria, Hair Algae and Bryopsis which commonly occur in outbreaks when there is too much nutrients in the water or the lighting is incorrect.

The benefits of macro-algae…



No one likes pesky micro-algae, but macro-algae on the other hand is very helpful and will be of great benefit to your aquarium by doing the following:

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 macro-algae:

Turtle Grass

Turtle Grass

Macro-algae 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 (usually a pretty slow process) 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 macro-algae:

1. Caulerpa species:



This rapid-growing and popular macro-algae comes from the phylum Chlorophyta which are the green macro-algae’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 macro-algae 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 macro-algae to have in your saltwater aquarium.

3. Coralline algae:

Corralline Algae

Corralline 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 macro-algae’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.

Using one of more of these species in your saltwater aquarium can also be your secret weapon to keep your water clean, healthy and pest algae free!

Saltwater Aquarium Advice