FAQ - Marine Macro Algae

Frequently Asked Questions - FAQ about the Beautiful World of Marine Macro Algae.

Macro algae are commonly often just called Seaweed. Although a lot of macro algae species are edible we sell our macro algae just for the use in the marine aquarium, so don't be tempted by the great pictures, please.

Macro algae species are divided into three main algae species groups which are the red, green and brown macro algae.

The most common and widely available macro algae species are the green macro algae. Especially the different varieties of Caulerpa are easily available, as they are successfully used to reduce effectively the Nitrate and Phosphate Level in the aquarium water, to suppress nuisance micro algae, as they often grow very fast and are easy to keep.

The second biggest group are the red macro algae species, which often grow much slower than the green algae species, but they add beautiful colours to the marine aquarium and in our opinion, some species are so great looking that they can easily compete with harder to keep coral species.

The third largest macro algae group are the brown macro algae species, which are very rare to get, as they are not very often used, and more often seen as unwanted macro algae in the marine aquarium.

  • Macro algae will help to remove nutrients from the marine aquarium and so reducing the nitrate and phosphate levels in the marine tank.
  • Macro algae can help to reduce unwanted micro algae by outcompeting them in the aquarium setup
  • Many algae species will provide shelter for copepods and amphipods and help to increase the population.
  • Some algae species will be happily eaten by fishes and critters and therefore help to keep them happy and healthy.
  • Macro algae will give your aquarium a more natural look
  • Seahorses will love the benefit of additional hold fast and we can imagine you will enjoy this look as well much more than the look of an artificial addition.
  • Many macro algae species can compete with corals when it comes to the look of it, and are often much easier to keep too.
  • Macro algae will add beautiful colours to your marine tank setup.
  • Macro Algae will release additional oxygen into the water while growing.

For a macro algae tank we recommend the following guideline for the marine water chemistry:

This may be different for reef tanks or systems with a refugium
( sump ) macro algae setup.

As a general rule, this is for most macroalgae species we sell, but there will be some which will need different environments. If you are unsure please ask us before you order.

Temperature: Between 23-28 °C

PH: 7.9-8.2

Salinity: 1.024 - 1.025

Nitrate: Between 5-10 ppm

Phosphate: Below 1 ppm

Magnesium: Around 1200 ppm - 1350 ppm

Calcium: Around 400 ppm - 450 ppm ( important for calcified species)

Iron: Around 0.01 ppm

Iodine: around 0.04 ppm

If you like to know more about what nutrients macro algae need to grow successfully in your marine aquarium please have a look HERE

Macro algae will need primary good lighting plus Nitrate and Phosphate to grow.

Most species will grow well under a  Full Spectrum light or a lighting with a colour spectrum between 5000k to 10000k.

Daylight has a colour spectrum of 6500k, which will be good for most macro algae species.

Beside of the major nutrients Nitrate and  Phosphate they will need some minor nutrients like Iron, Sulfate, Biotin, Manganese and Iodine, which will normally be added with your regular water changes or can be added with separate trace element additions.

If you like to know more about Nutrients for Marine Macro Algae

For most marine macro algae a full spectrum lighting is a great solution to keep them successful in the tank. In general, a lighting with the light colour spectrum between 5000k - 10000k is sufficient, we recommend so a 6500k lighting, which is great for most macro algae species. In our macro algae data sheet, you will find information regarding the special needings of the individual macro algae species.

We recommend 2-4 watts of PC or more per gallon of water in your aquarium setup which will be sufficient for most macro species in a standard depth tank.

While the light intensity is measured in output rather than watts, it is often very hard to determine the output of a particular light source, and therefore it is often more helpful to use watts as a more useful secondary measuring method.

Some algae, especially fast-growing algae like some Caulerpa species need regular trimming, which is as well perfect to effectively remove the nutrients from the tank.
Other macroalgae, especially the red macroalgae species grow slower and need more rarely trimming.

You will find for every macro alga we offer on the individual species website instructions how to care about the algae species best.

Adding marine macro algae to a new water environment means that the macro algae will need some time to adjust to the different water conditions, which means to a different salinity, water temperature, ph, alkalinity, nitrate and phosphate levels.

This can mean that parts of the algae first will die off before it will start to grow back again.

Keep an eye on the macro algae and remove just the parts which turned transparent.

Should you have still problems please just contact us.

Especially when it comes to some marine macro algae of the species Caulerpa you will across the words sporulation or "going sexual".

Which means nothing else that the algae are dying off and the start of the reproduction cycle, 

This mainly with Caulerpa species know process can happen when the water parameters or condition changed very fast, like the essential trace elements Nitrate & Phosphate, the water temperature, the salinity, alkalinity or ph levels.

Therefore it is important to keep the water conditions as constant as possible and to remove any dead parts of the macro algae as soon as possible.

We keep caulerpa species since more than 14 years successfully in our tanks without any problems.

But should it have happened a large water change is highly recommended?

If red marine macro algae are going to dark it is often a sign of not enough light, whilst a very bright red or a white colouration is a sign of too much light( often visible at the grapes of the red grape macro ).

Just vary the location of the macro algae in your tank and let it adjust for a couple of days to see if the lighting conditions are better for the macro algae.

We recommend for smaller reef tanks and Nano-Tank setups especially marine macro algae which are non-invasive and slower growing. 

Especially a lot of red marine macro algae species are perfect for those conditions. 

Have a look at our section for Nano-Tanks, where we added all the macro algae species which will do great in there.

Macro Algae for Nano-Tanks and smaller Reef Tanks

Yes absolutely. We have an extra section for marine macro algae which we recommend for them. It will provide them with a natural holdfast and more comfort to keep them happy and healthy in your Seahorse Tank. And we are sure you will enjoy it too, as it looks just so much more natural than any artificial solution.

Macro Algae for Seahorses

Assumed that you have a suitable light for your macro algae above your sump we would recommend the following macro algae species:


Sometimes it won't grow in some marine tanks, in this case, we recommend the following Caulerpa species, which might need a bit more attention than Chaeto, but we use them since many years without any problems so far.


We have created a selection of marine macro algae which we know are often happily eaten by marine fishes.

But please keep in mind that we can't guarantee that your fish will like the macoalgae too, as marine fishes have different behavings and personalities as they have a different taste too.

Macro Algae Great for Feeding

We have lots of hermit crabs and snails and they take normally just care about the nuisance algae, like green hair algae or film algae. But it might be, that they will eat the macro algae, depending which species you get, before they starve :) Which I prefer.

Well, this is very hard to answer. As we will all have a different taste when it comes to the look and the beauty of marine macro algae.

We love macro algae, so we see the beauty in almost all species we have. But we know how friends react when they see our private reef tank with the different marine macro algae.
And it is quite funny, as they sometimes can't tell the difference between a coral or algae. ( surely no experts... just friends :) )

There are some macroalgae which look really stunning in our reef tank, and we would choose them as our favourites when it comes to the beauty of them:


Macro algae will need a more stable water environment, as some algae can get damaged when values like alkalinity or PH swing too much.

As well they will need a sufficient amount of nitrate and phosphate in the marine water to thrive which often is not present to start with.

We would therefore not recommend adding macro algae in a new marine aquarium setup, especially when it is just a few weeks old, as the aquarium will be still in the cycling process. 

As well can especially in the first weeks of a new marine aquarium nuisance micro algae overgrow your new macro algae, as some micro algae can double their size within just 24 hours.

After you added some fishes give it a few weeks more and it will provide a much better environment for the new marine macro algae to keep them successful and thriving. 

This will be different when you have a planted marine tank and you use special fertilizer to your water, to add the necessary elements for the macro algae.

We recommend for the Triton Method TM  to use marine macro algae which are fast growing.

Have a look at the following category please:

Macro Algae for the Triton Method TM

As you like to change it a planted tank I would recommend you might want to have a look into some invasive macro algae species nonetheless again, as they will give an amazing natural look. And unfortunately, they grow much faster than most non-invasive macro algae.
If this would be alright for you I would recommend the following algae species, as they just have the benefit to grow fast and will provide the basic layer for a planted tank setup in my opinion.
Not too fast-growing species are for example CAULERPA PROLIFERA as they will look great with their long blades. 
And other great algae for this is the CAULERPA TAXIFOLIA , which will grow a bit faster than the Prolifera algae species, and it will need a bit more light too.
And last but not least CAULERPA RACEMOSA GRAPE ... just a great looking algae species.
But if these are not fitting in your planted marine setup ideas, I would recommend those algae species
As a centrepiece and still medium fast growing the BOTRYOCLADIA - RED GRAPE is a perfect alga.
OCHTODES SP. will add some blue/violet colour and is not very invasive, as it will grow nice and big, but won't spread like Caulerpa algae species.
ULVA LACTUCA is medium fast growing again, but looks really beautiful, have a look at the picture :)
CHLORODESMIS SP. is often overseen in a planted tank, as many misses understand this alga as a micro algae, but it has a much harder structure and looks stunning once grown bigger, like a big lawn, which needs cutting after a while like the real one:)
The RED TURF MACROALGAE will add another beautiful red colour and it is a bit faster growing than Ulva or Red Grape Algae species.
HALYMENIA DURVILLEI DRAGONS not mentioned before, but stunning looking, It grows slower, and we had recently some problems with it, but it is nicely growing back now, and soon ready to sell again.
GRACILLARIA CURTISSAE is another slow-growing one, actually very slow growing but it will stay compact, and shouldn't be left out.
And maybe some CODIUM and HALIMEDA INCRASSATA . The Halimeda needs so a bit higher calcium levels and prefers a place in the substrate.

Yes, there are a few species which will do well in a sand bed. Especially caulerpa macro algae species like caulerpa prolifera, caulerpa taxifolia and caulerpa racemosa will do very well. But as they are fast growing they will need trimming back, or there is a risk that they can overgrow your main tank.

Other macro algae like the Halimeda Species are very good as well for the substrate, but they will stay more in the spot you placed them.

Slow growing red macro algae species like the Gracileria or Codium species can be mounted on a small rock frag and will look great too, but won't be invasive as the caulerpa species.

For an effective and fast nutrients export, which means the reduction of the Nitrate and Phosphate in your marine aquarium water, we recommend macro algae which will grow fast, like a lot of Caulerpa Algae Species.

You will find them here:

Macro Algae For Nutrients Export

Our other macro algae species will take nutrients out of the water as well, but as they often grow slower they will take out less Nitrate and Phosphate than the recommended species. On the other hand, those macro algae species are often non-invasive and therefore better qualified to use them in the marine tank display.

If you have any questions to choose the right macro algae for your marine aquarium don't hesitate to contact us.

Livealgae UK

Especially in marine macro algae dominated marine tank setups it can be necessary to add Nutrients like Nitrate & Phosphate, Iron and other trace elements.

Especially Iron can support the growth of marine macro algae and can be safely added to the marine aquarium, following the instruction of the used Iodine solution.

There are some readily mixed solutions for most necessary nutrients available - often for freshwater plants - which should be used just for a closed planted marine aquarium tank, as it might be that some of the added trace elements are harmful to your critters or livestock.

Invasive macro algae are algae species which will attach easily themselves and need therefore more attention than non-invasive macro algae

Especially some Caulerpa species are growing very fast and can easily attach themselves to live rock, where it can be hard to remove again, as often just a tiny part of it can be enough to grow back again. As well there is a risk that it might overgrow your corals.

We recommend keeping invasive macro algae species very restrained in the tank display, or better in the refugium/sump of your marine reef tank.

As invasive macro algae species often grow very fast they are a favourite choice of marine macro algae when it comes to nutrients export and for the Triton Method TM.

Marine macro algae will release without light some Corbondyocide CO2 into the marine aquarium, whilst with light, it will produce oxygen. 

In heavily algae planted marine tanks it is recommended to keep the light for the algae on 24/7, which will work with most algae species.

For Herbivore and Omnivore fish species, it will provide additional health benefits, as they will need marine algae to stay happy & healthy. 

Often a discolouration of some Tang fish species is a sign of a algae deficit in the food provided.

Yes, they can! And therefore dying parts of should be removed from the tank. Especially some Caulerpa macroalgae species should be watched closely. Please read more  about them in the extra point Caulerpa Case

We are sorry, but all macro algae we sell are just for Marine Aquarium setups. We don't have any plants for a tropical fish tank, unfortunately.

Yes, we are always looking for marine macro algae species which we don't have or which might be low on stock ( marked as regrowing ).

If you have those algae we would love to hear you and either buy them from you or swap them against another macro alga you like to have.

It varies, we have some macro algae which we would recommend more for the sump, as they are invasive marine macro algae species, but we have a lot of marine algae which is just perfect for the tank display and will stunning colours and natural beauty to it. 

It will depend on what macro algae you are looking for to attach. Most of the non-invasive species, like the very popular Red Grape species, can be easily attached by using normal cyanoacrylate super glue ( we personally prefer the Gel variation and our favourite brand is Loctite Super Glue Universal Gel).

A drop if it on a wet piece of rubble or similar will be enough to keep most algae in place. (We recommend to dip it before placing it in your aquarium in some marine water)
Some people prefer to use a rubber band to keep the algae in place, or some just place it between some rock pieces.
Macroalgae like the beautiful Ochtodes will attach themselves, but they will need a few days to do so. Here again, a drop off glue can be very helpful for the start.
Other algae species like most Caulerpa macroalgae species are self-rooting, so they are best placed in the sump, or in the Tank Display with caution, as they can overgrow the rockwork/corals, when not kept restrained, and it can be a pain to remove them from the rock again, once they have attached themselves. 

Some planted marine aquarium owner enthusiasts have this actually as a goal, as it gives a fantastic natural look to the aquarium.
Chaeto / Chaetomorpha is best placed in the sump btw.

Frequently Asked Questions

Do you have a shop to visit?

As an aquatic algae farm, we don't have a public shop to visit unfortunately but we are happy to post all our macro algae species within the UK for free to you.

And we are sure you will like your new macro algae addition once received.

How do I know when a algae is back in stock?

You can register your interest on the algae page you are looking for to get an email once it is back in stock or stay informed via our Newsletter, and or to follow us on Facebook, as we will first inform there when our algae are ready to sell again, or when we received new macro algae species.


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What means "Regrowing"?

When a macro algae species sells well we have sometimes to take it out of the sale as it will need time to regrow again.

The time for this will vary, as some macro algae species will grow very slow, whilst other - especially various  Caulerpa marine macro algae species grow quite fast.

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Therefore we offer you a hassle free 100% Satisfaction Guarantee.
If you are not happy with your purchase we will refund your money back (UK Orders only).

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