FAQ - Marine Macroalgae

What are the different types of macroalgae?

Macroalgae are commonly often just called seaweed. Although a lot of macroalgae species are edible we offer for sale all macroalgae species just for the use in the marine aquarium, so don't be tempted by the great pictures, please.

Macroalgae species are divided into three main live algae species groups which are the red macroalgae, green macroalgae and brown macroalgae.

The most common and widely available macroalgae species are the green marine algae species. Especially the different varieties of Caulerpa are widely available as they often grow very fast and are easy to keep. They are successfully used to reduce the Nitrate and Phosphate level in the aquarium water, which can help to suppress nuisance microalgae.
The only downfall with green macroalgae species is that they are often invasive, which means that they can overgrow your rockwork when not kept under control. Often they are placed in a Refugium / Sump to let them do the nutrients export work and to keep them in a controlled area.

The second biggest group are the red macroalgae species, which often grow much slower than the green marine algae species, which means that they take less nutrients ( Nitrate / Phosphate ) out of the water but therefore they add some beautiful colours to the marine aquarium and in our opinion, some species are so good looking that they can easily compete with harder to keep coral species.
But the best they are often non-invasive and therefore just perfect to be placed in the Display Tank.

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

What are the benefits of marine macroalgae?
  • Macroalgae will help to remove nutrients from the marine aquarium and so help to reduce the nitrate and phosphate levels
  • Macroalgae can help to reduce unwanted microalgae ( nuisance algae ) by outcompeting them in the marine tank
  • Many macroalgae species will provide shelter for copepods and amphipods and help to increase the population, especially Ochtodes, Chaetomorpha etc.
  • Some macroalgae species will be happily eaten by fishes and critters and therefore help to keep them happy and healthy, like Ulva.
  • Macroalgae 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 macroalgae species can compete with corals when it comes to the beauty of it, and are often much easier to keep too.
  • Macroalgae will add beautiful colours to your marine tank setup.
  • Macroalgae will release additional oxygen into the water while growing.

What water conditions will need macroalgae to grow?

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

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 23-29 °C

PH: 7.9-8.4

Salinity: 1.024 - 1.026

Nitrate: Between 5-10 ppm, above 2ppm

Phosphate: Below above 0.02ppm

Magnesium: Around 1250 ppm - 14000 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 macroalgae need to grow successfully in your marine aquarium please have a look HERE

What does macroalgae need to grow?

Macroalgae will need primary good lighting plus Nitrate and Phosphate to grow, beside of a few minor minerals.

Most live algae species will grow well under a  full spectrum light or a lighting with a colour spectrum between 5000k to 8000k.

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

Beside of the major nutrients nitrate and phosphate marine algae 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 Macroalgae

What light do I need to grow macroalgae?

For most marine macroalgae a full spectrum lighting is a great solution to keep them successful in the reef tank. In general, a lighting with a light colour spectrum between 5000k - 8000k is sufficient, whilst we recommend a 6500k lighting, which is great for most macroalgae species.

In our macroalgae data sheet, you will find information regarding the special needs of each individual macroalgae species.

We recommend 2-4 watts of PO or more per gallon of water in your marine aquarium setup which will be sufficient for most macro algae 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.

Do I have to trim macroalgae back?

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

When green macroalgae species turn white oy yellowish, or lose their structure and turn "mushy" they should be removed / cut off to avoid nutrients getting back into the aquarium.

Where to place the macroalgae in the display tank?

The best place or the macroalgae will depend on the macroalgae species you like to add to the marine tank, as they will need different light intensity and waterflow often.

To make it easier for you we have therefore added for every macroalgae species on the product page this information for you. 

Help. my macroalgae is not growing!

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

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

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

Should you have still problems and your water parameters are in the range as we recommend please don't hesitate to contact us as we are happy to help you.

What does sporulation or "going sexual" from Caulerpa algae mean?

Especially when it comes to some marine macroalgae of the species Caulerpa you will come across the words sporulation or "going sexual", which means nothing else than that the caulerpa marine algae is dying off and starts a reproduction cycle, which than often is clearly visible as it turns the water milky cloudy, depending on the amount of caulerpa species which has died off.

The sudden die off of Caulerpa species is a known process which rarely happens, but it may be triggered by sudden/massive changes of water parameters of the water temperature, the salinity, alkalinity or ph levels.

Therefore it is important as always in this fantastic marine aquarium hobby to keep the water conditions as constant as possible and to remove any dead parts of the macroalgae as soon as possible.

Should it have been triggered we recommend a large water change of 25% and more. 

This said we keep caulerpa species since more than 16 years successfully in our macroalgae tanks without any "going sexual" event at all.

This problem won't btw not happen with most other macroalgae species, like Ochtodes, Ulva, Gracilaria etc. 

My red macroalgae is changing its colour?

When red marine macroalgae are turning more bright red it is often a sign of too much light, whilst a more white or orange colouration often is a sign that those parts die off.

More faster growing macroalgae species like Red Grape will develop more pale grapes for example when it gets too much light.

We recommend to vary the location of the macroalgae in your tank and let it adjust for a couple of days to see if the lighting conditions are better for the macroalgae.

Can i use macroalgae in a small reef tank / nano-tank ?

Absolutely :) We recommend for smaller reef tanks / Nano-Tanks because of the limited space marine macroalgae species which are non-invasive and slower growing. 

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

Please have a look at our section for Nano-Tanks, where we added all the macroalgae species which will do just great in a smaller aquarium.


Would you recommend macroalgae for a Seahorse tank?

Yes absolutely! They will love most macroalgae additions. We have therefore added an extra section for marine macroalgae which we recommend especially for a Seahorse aquarium. 
Macroalgae will not just provide for Seahorses beautiful natural holdfasts to keep them happy and healthy, but also improve the water quality by adding more oxygen and cleaning the water when growing

Beside of this some macroalgae with a dense structure like the Ochtodes or Green Bush live algae species will offer as well great hiding spaces for copepods and Rotifers and Seahorses love to use this as a hunting ground :).

And we are sure you will enjoy it too, as it looks just so much more natural than using artificial solutions where they hold onto.


What macroalgae species are good for the sump / refugium?

Assumed that a suitable light for macroalgae is already installed in the refugium / sump we would recommend the following marine macroalgae species:

The most often macroalgae species as it is very easy to grow:


And if you like to create a planted refugium we do recommend the following Caulerpa species, which will need a bit more attention than Chaetomorpha as they can go sexual. See more about this here in the FAQ section.


Which macroalgae would you recommend to feed my Yellow Tang Fish?

We have created a section of marine macroalgae, which includes those kind of macroalgae which are very often eaten by herbivorous marine fishes like Tang fishes, Foxface fishes etc.

Please keep in mind though that we can not guarantee that your fish will like the macroalgae too, as marine fishes have different behaviors and personalities as they have a different taste too.


Will hermit crabs eat the macroalgae in my tank?

We have lots of hermit crabs and snails in our macroalgae tanks and they normally just care about the nuisance microalgae, like green hair algae or film algae.  But it might be that they will eat the macroalgae, depending which species you get, before they starve.

What types of macroalgae are the more attractive varieties?

Well, this is very hard to answer. As it depends of course on your personal taste, especially when it comes to the look and the beauty of marine macroalgae.

We love macroalgae, so we see the beauty in almost any macroalgae species we have. But we know how friends react when they see our private reef tank with the different marine macroalgae

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


Can I add macroalgae to a new marine aquarium?

Macroalgae will need a stable water environment, as some live algae species can get damaged when water parameter like alkalinity or pH swing too much.

As well macroalgae need a sufficient amount of nitrate and phosphate in the marine water to thrive which often is not present to start with in new tanks without livestock, eg fishes or seahorses

We would therefore not recommend to add macroalgae to a new marine aquarium setup, especially when it is just a few weeks old and the cycling process hasn't been finished. 
Especially as in the first weeks of a new marine aquarium nuisance micro algae may easily overgrow your new macroalgae, as some microalgae can double their size within just 24 hours.

After you have added some fish, give it a few weeks more and your new marine aquarium 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 newed marine tank and you use special fertilizer to your water, to add the necessary elements for the macroalgae of course.

What macroalgae do you recommend for the Triton Method ?

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

Have a look at the following category please:


Are there any macroalgae which can be planted in the substrate in the display tank?

Yes, there are a few macroalgae species which will do well in the substrate. Especially caulerpa macroalgae species like caulerpa prolifera, caulerpa taxifolia and caulerpa racemosa will love this. But as they are fast growing they will need to be restricted, or they can overgrow the whole reeftank.

Other macroalgae like the Halimeda species are very good too  for the substrate too and will stay more in the spot where placed.

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

What macroalgae would you recommend to lower my nitrate & phosphate levels in my tank?

For an effective and fast nutrients export in the marine tank, which means the reduction of the nitrate and phosphate in the marine aquarium water, we recommend mainly macroalgae which will grow fast, like a lot of Caulerpa macroalgae species.

You will find them here:


Our other macroalgae 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 fast growing macroalgae species. On the other hand, those slow growing macroalgae species are often non-invasive and therefore better qualified to use them in a marine display tank.

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

What does dosing macroalgae mean?

In a macroalgae reef tank or planted refugium /sump it can be necessary to add nutrients like nitrate & phosphate, Iron and other trace elements to keep macroalgae healthy and well growing, especially when the macroalgae growth is not satisfying, or dying off and very often in marine macroalgae dominated reef tanks. 

Dosing nutrients can be as well very helpful to stimulate macroalgae growth in generell.

Beside of the main nutrients macroalgae will need to grow ( nitrate, phosphate ), Potassium, Iodine and Iron will support the growth of marine macroalgae too and can be safely added to the marine aquarium, following the instructions provided.

If you like to know more about dosing macroalgae in a reef tank you can find more about  HERE

Livealgae UK offers as well a range of fertiliser and additives for an optimized macroalgae growth, which you can find HERE

We do not recommend to use fertiliser for normal planted aquariums, as they are often produced to use in freshwater aquariums and often include ingredients which can be harmful to marine life like critters, livestock and corals, especially when Copper has been added to it.

There are some readily mixed fertilisers available which are safe to use as they are specifically formulated for marine tanks, like Brightwell's ChaetoGro and Continuum's Basis Chaeto Grow 

What are invasive macroalgae species?

Invasive macroalgae species will attach easily themselves to rock etc. and need therefore more attention than non-invasive macroalgae as they might easily overgrow the rockwork where they will be often hard to remove from again, as just a tiny part of it can be enough to grow back again. . 

Especially some Caulerpa macroalgae species are growing very fast and can easily attach themselves to live rock, causing as well the risk that it might overgrow your corals too.

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

Of course in a dedicated planted reef display tank they almost are a must have macroalgae in there :)

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

Can macroalgae harm fishes?

Marine macroalgae will release without light some Carbon Dioxide CO2 back into the marine aquarium, whilst with light turned on it will produce oxygen. 

In a heavily macroalgae planted macroalgae refugium it is therefore recommended to keep the light on for the macroalgae anti clockwise. Which means turned on over night and turned off over the day.

For herbivore and omnivore fish species macroalgae will provide as well additional health benefits, as it will offer a natural source of live algae which they need to stay happy & healthy. Often a discoloration of some Tang fish species is a sign of an algae deficit in the food provided, where live algae can help to avoid this.

Can macroalgae leech nitrate / phosphate back into the water?

When macroalgae dies off it will leech back the nutrients it has taken out of the water before to grow. 

Therefore dying parts of macroalgae species should be removed from the tank as soon as possible. Especially some Caulerpa macroalgae species should be watched more closely. Please read more  about why here Caulerpa Case

Can macroalgae be used with tropical fish?

We are sorry, but all macroalgae we offer for sale are just for marine aquarium setups. We don't have any plants for a tropical fish tank, unfortunately.

Do the macroalgae go in the sump / refugium or can they be placed to the display tank too?

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

How do you attach the macroalgae?

It will depend on what macroalgae 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 ).

A drop if it is on a wet piece of rubble or similar will be enough to keep most macroalgae in place. (We recommend to dip it before placing it in your aquarium in some separate marine water)
Some people prefer to use a rubber band to keep the macroalgae 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 in an area without much current but good lighting. 
Here again, a drop off glue can be very helpful for the start.
Other macroalgae 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.

Do you buy marine macroalgae?

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

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

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