Macro Algae for Sale in Australia

Macro algae is the least glamorous and most reliable nutrient control there is. It grows, it takes nitrate and phosphate out of the water while it does, and you throw the excess away. No dosing, no consumables, no reactor.

Gallery Aquatica grows out and sells macroalgae from our shop in Tingalpa, Brisbane. This page covers what to buy, how to run it, and what to know before ordering live macroalgae in Australia. If you already know what you want, browse the macroalgae range.

What macro algae actually does

Nitrate and phosphate accumulate in a closed system because you keep adding food and nothing removes the end products. Water changes dilute them. Skimmers pull out some of the organics before they break down. Macroalgae does something different: it absorbs the dissolved nutrients directly and builds them into plant tissue.

That tissue is the point. When you harvest a handful of chaeto and bin it, the nitrogen and phosphorus locked up in it leave the system permanently. That is genuine export, not conversion, and it is the reason a refugium keeps working month after month without you buying anything.

Two secondary benefits people underrate. Macroalgae competes directly with nuisance algae for the same nutrients, and a well-established refugium often starves hair algae out of the display. And a dense clump of chaeto is the best copepod habitat you can put in a tank, which matters if you keep anthias, mandarins or anything else that grazes live food.

The macroalgae we grow and sell

Availability moves around, because it depends on how much has grown out since the last harvest. If you want a particular one, it is worth ringing 0420 484 584 before ordering.

Chaetomorpha

Chaeto is the default and, for most tanks, the right answer. It is a coarse, wiry green algae that grows as a loose ball, does not go sexual and crash the way some caulerpas can, and does not attach itself to your rockwork. It tumbles in flow, which keeps every strand lit and growing.

It is also the easiest to harvest: pull out a handful, bin it, done. Available as a bag of chaetomorpha, or as part of a refugium start-up pack if you are setting up from scratch.

Branching coralline algae

Different animal entirely, and worth understanding before you buy. Coralline is a calcifying red algae - the hard purple-pink crust that spreads over rock and glass in a mature reef tank. Branching coralline grows as a small three-dimensional bush rather than a crust.

It is not a nutrient-export tool. You buy it because it looks good and because it seeds the tank, so coralline spreads onto your own rockwork over the following months. It uses calcium and alkalinity as it grows, so it wants stable parameters rather than high nutrients. Available as an aquacultured branching coralline chunk or frag.

Caulerpa

Caulerpa species are fast, attractive and genuinely effective at stripping nutrients - faster than chaeto in most systems. The trade-offs are real though. Caulerpa attaches by runners and will spread into the display if it gets the chance, and some species can "go sexual", releasing spores and dying back in a way that dumps everything they absorbed straight back into the water. Running the refugium light continuously, rather than on a cycle, reduces that risk.

One important point for Australian buyers. Caulerpa is a regulated genus in parts of Australia. Caulerpa taxifolia is a declared noxious species in several states, and the rules covering other Caulerpa species vary between states and territories. We do not stock taxifolia, but if you are ordering Caulerpa from outside Queensland, check your own state or territory's current requirements first, and email us before you order so we can sort it out with you. We would rather have that conversation up front than send something that cannot legally be received.

Currently available as aquacultured Caulerpa racemosa.

Halimeda and others

Halimeda is a calcifying green macroalgae that grows in flat segmented discs and looks like a small underwater cactus. It is decorative rather than a workhorse - it grows slowly and exports less than chaeto - and it draws on calcium and alkalinity. It comes in and out of stock depending on grow-out. Ask us what is currently available.

Which one should you buy?

For nutrient export, buy chaeto. It is the cheapest, hardiest and least troublesome, and nothing else is meaningfully better at the job. If you are starting a refugium from nothing, the start-up pack saves assembling the pieces separately.

For appearance and to seed your rockwork, buy branching coralline, and understand it is doing a different job.

Buy caulerpa if you want faster growth and are prepared to manage it - and read the note above about state rules first.

Running a refugium

A refugium is just a lit section of sump where the macroalgae lives. It does not need to be elaborate.

Light. This is the part people underdo. Macroalgae wants a lot of light, and cheap full-spectrum LED is fine - it does not need reef-grade hardware. Many people run the refugium light on a reverse cycle, on overnight while the display is dark, which steadies pH across the 24 hours because something in the system is always photosynthesising. With caulerpa specifically, a continuous light is often preferred to reduce the chance of it going sexual.

Flow. Enough to tumble the chaeto slowly. If the ball sits still, the underside shades out and rots; if the flow is fierce, it shreds. A gentle roll is what you want.

Harvesting. This is the actual nutrient export and skipping it defeats the purpose. When the chaeto has roughly doubled, pull out about half and throw it away. Every few weeks is typical. Chaeto that has stopped growing has usually run out of something - often iron - which is what a supplement like Chaeto Grow addresses.

What can go wrong. Macroalgae can strip nutrients too far. Nitrate and phosphate at zero is not the goal - corals need some, and a tank bottomed out on both often shows pale tissue and, ironically, an outbreak of dinoflagellates. If your numbers are falling toward nothing, harvest less or reduce the refugium photoperiod.

There is more detail on setting one up in our guide to chaetomorpha, refugiums and macroalgae.

Buying live macro algae in Australia

Macroalgae is a living thing, so it is handled differently from dry goods. Stock depends on grow-out rather than on a warehouse, and how it travels to you depends on where you are.

Delivery arrangements for live goods, including packing and which services are used, are set out on our freighting and packing page. If you want to know what is possible to your specific address, the fastest answer is to email shop@galleryaquatica.com.au and ask - that gets you a real answer rather than a guess.

You are also welcome to pick up in person from the shop in Tingalpa, about fifteen minutes east of the Brisbane CBD. Details are on our Brisbane store page.

Common questions

What is macro algae?

Macroalgae is algae large enough to see and handle as a plant - chaetomorpha, caulerpa, halimeda and similar - as opposed to the microalgae and film algae that grow on glass. In a marine tank it is grown deliberately, usually in a refugium, to absorb nitrate and phosphate.

Does macro algae really remove nitrate and phosphate?

Yes, and it is one of the few methods that removes them permanently rather than converting them. The algae builds the nutrients into its own tissue as it grows, and harvesting that growth takes them out of the system for good. Growth rate is the limiting factor: algae that is not growing is not exporting.

What is chaetomorpha?

A coarse, wiry green macroalgae that grows as a loose tumbling ball. It is the most widely used refugium algae because it does not attach to rockwork, does not readily go sexual, and is very easy to harvest.

Do I need a refugium to keep macroalgae?

It is the usual approach, but not compulsory. Macroalgae needs light and flow, so any lit section of sump works. Some people grow it in a hang-on box or even in the display, though in the display it competes with your aquascape for space and light.

What light does macroalgae need?

Plenty of it, but not expensive light - a cheap full-spectrum LED is fine. Many keepers run the refugium light on a reverse cycle, on overnight while the display lights are off, which helps hold pH steadier across the day.

How often should I harvest chaeto?

When it has roughly doubled, remove about half. For most tanks that is every few weeks. If you never harvest, you stop exporting nutrients and the refugium becomes decoration.

Why has my chaeto stopped growing?

Usually it has run out of something. Iron is the most common shortfall, which is what chaeto-specific supplements address. Not enough light and too little flow are the other two usual causes. Occasionally the opposite is true and the tank simply has no nutrients left for it to consume.

Is coralline algae the same as macroalgae?

No. Coralline is a calcifying red algae that grows as a hard crust or a small branching bush. It is decorative and it seeds your rockwork, but it does not export nutrients the way chaeto does, and it consumes calcium and alkalinity as it grows.

Can I buy macro algae online in Australia?

Yes. It is a living product, so availability depends on how much has grown out since the last harvest, and delivery is handled differently from dry goods. See our freighting and packing page, or email us about your specific address. Some Caulerpa species are regulated in parts of Australia - check your state's requirements before ordering.

Can macroalgae remove too much nitrate?

It can. Zero nitrate and zero phosphate is not the target - corals need some nutrient, and a bottomed-out tank often shows pale coral and a dinoflagellate outbreak. If your levels are heading to nothing, harvest less often or shorten the refugium photoperiod.

Browse the range

See the full macroalgae range, or the invertebrates and coral ranges. For nutrient control on the equipment side there are protein skimmers, filtration and test kits.