The Salty Side: Saltwater Aquariums for Beginners

Nori for Saltwater Fish: What is Nori and How do I Give it to My Fish?

If you’re new to reef aquariums you may have read that a lot of reef aquarium owners give nori to their saltwater fish.  Well, I’ve dedicated a whole article to nori, what it is and how to feed it to your saltwater fish.

What is Nori?

Dried or roasted seaweed is also known as ‘nori’.  The word ‘nori’ is Japanese for ‘edible seaweed’1 which may also be referred to as laver.  You may know it better as the green edible wrapper used in making sushi.

There are mainly three types available, red, green and brown.  Green is the most popular type of dried seaweed fed to saltwater fish and invertebrates.  Nori is a dried macroalgae and is purchased in sheet form in sealed packaging.

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Why Give Dried Seaweed to Saltwater Fish?

Nori, or laver, is known for it’s rich vitamin and mineral content such as Vitamin A, Vitamin B1 and Vitamin B12, thiamine, riboflavin, and tocopherols3.  It also contains essential amino and fatty acids which are all important for keeping fish healthy. 

It is a great source of iodine
2 too, which is converted by fish into thyroid hormones.  Goitre is a common result of a lack of iodine in fish so the addition of dried seaweed to a reef tank would be very beneficial.  And not only to fish!  Invertebrates that have run out of algae to feed on in a saltwater aquarium will need dried seaweed as a supplement.  If not, it could lead to starvation. 

Which Saltwater Fish Eat Nori?

Algae eaters, herbivores and omnivores, such as tangs, surgeonfish, angelfish, wrasse and parrotfish love dried seaweed.  Although be prepared, some are fussier than others as to what type of nori they eat!  Algae blennies will also graze on the dried seaweed as well as chromis, once the larger fish have managed to break off chunks for them.

As mentioned above, it is also used to supplement the diet of snails, crabs and urchins.  This can be crucial when there is insufficient algae left in a reef tank for fish and invertebrates to feed on.  In fact, a lack of algae is one of the reasons that an urchin may start losing it’s spines.    

When and How Much Do I Feed My Fish Nori?

I feed dried seaweed to my saltwater fish once per day

I use the Gourmet Grazer to feed my fish nori but you can also use pouch feeder or nori clip.  I cut a sheet of nori into five strips with a pair of scissors.  I then fold 2 strips until it small enough to place it in the Gourmet Grazer (or pouch feeder/nori clip). You may want to remove any leftover food after a few hours as it can cause an increase in nitrate/phosphate levels.  If you are concerned that there may be higher levels of nitrates or phosphates due to overfeeding then simply reduce the amount of nori. 

I personally don’t need to remove any leftovers because quite simply, there aren’t any!  I find that two strips is enough for the inhabitants of my 125 gallon (560 litre) tank.  

How Do I Give Nori To My Saltwater Fish

The best way I’ve found to give nori is with the Gourmet Grazer.  I find the Gourmet Grazer way superior as it holds the seaweed in place and don’t fall apart.  Once it gets wet it starts to disintegrate and can be pulled off in huge chunks.  Fish will chase after it but it tends to be messy and may also get stuck in the filter. 

If you don’t have a veggie clip or pouch feeder you can also try tying some seaweed to a small piece of rock with an elastic rubber band.  Some reef tank owners use fishing line to lower the rock into the tank and then remove it when the fish and invertebrates have eaten the nori.

How Is Nori Made?

Dried seaweed was first harvested and dried in Japan.  Seaweed is grown on large nets in the ocean and when it has grown sufficiently it is harvested.  The seaweed is then washed and filtered ensuring that it is as clean as possible with no contaminants.  It is rolled into sheets, excess water removed and cut to size.  Any residual water that may still be present is removed through a heating process and the dried sheets are cut and packaged ready to send to suppliers. 


Make sure the nori has no added flavours.  You don’t need to get expensive brands marketed at the marine fishkeeping world.  As long as it has no added flavours or enhancers, it should be fine to use in your tank.  The seaweed can be roasted or dried.  I personally use roasted as this is what my saltwater fish are used to and it’s available locally.  Some fish are fussy though and have their preferences.  I tried switching to a cheaper brand of dried seaweed to the one I was currently giving my saltwater fish and well, let’s just say they have expensive taste!

Hi, my name is Craig.
I am the owner of The Salty Side.
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