What Is Nori and How Is It Used?

Feeding Nori to Saltwater Aquarium Fish and Other Algae Eaters

Nori is most often used as a wrapper for rolled sushi. PhotoAlto/Ale Ventura/Getty Images

Nori is natural seaweed that is roasted or dried, and believe it or not is actually a human food consumption item used in oriental cooking. In particular, the roasted type is most often used as wrappers for making rolled sushi, while the dried type may be used for this purpose as well as making seaweed soup and rice balls. Nori is sold under many different names, just look for roasted or dried seaweed on the package.

What is nori, and how is it used?

When marine aquarists discovered the nutritional value of nori, being high in carbohydrates, protein, vitamins, and especially minerals, they began using it to feed their saltwater herbivores. It is ideal for feeding tangs and surgeonfishes, some angelfish and blenny species, as well as many other types of algae eaters like hermit crabs and snails.

There are usually two kinds of nori to choose from, red, which sometimes looks dark purple in color, and green, but occasionally fish stores may carry a brown type that is often favored by some surgeonfish species. It usually comes packaged in full sized sheets, but you may find it already cut up into pieces and prepackaged by some aquarium stores or suppliers. We have always bought nori from the oriental food section of our local grocery store, packaged in 10 - 8 inch x 8 1/2 inch sheets. Our preference is towards the green kind because it seems to dissolve more slowly than the red, making feeding with it a little less messy.

Be careful when buying nori in grocery stores. Flavored types are sold, such as teriyaki, and you want to avoid these.]

Having used nori to feed our captive marine life since 1989 with no problems, it is interesting that we have heard mention that this product may introduce phosphates into aquariums.

For this reason, some aquarists do not recommend it as a food source, but if you are concerned about this potential problem, there is a simple solution. Before you start using it, just run a test on the aquarium water to check and see if the phosphate level is acceptable, then perform tests regularly over a period of time after you begin feeding with nori to see if it may be contributing to a PO4 build up in your system.

  • It is important to NOT overfeed, as any excess nori that is uneaten may contribute to the lessening of the water quality in the aquarium.
  • Only feed what the tank inhabitants will consume in a short period of time, removing any excess nori that may be floating around in the water or that settles on the bottom of the tank uneaten after an hour or so.
  • To enhance its nutritional value, you can option to apply a few drops of a liquid vitamin supplement such as Selcon onto the dried nori and allow it to soak in before feeding.
  • Any unused nori should always be kept dry and stored in an airtight container! It WILL absorb moisture from the air, which particularly in high humidity regions may cause it to become damp and grow mold on it, making it unusable.

How To Feed Livestock Nori

Something to remember when you first start to feed your fish and other tank inhabitants nori is that often they are afraid of it to begin with because they are not used to seeing something strange drifting or waving around in their tank. They may avoid it until they get used to seeing it and figure out that it is food.

If using nori in the full sheet form you can:

  • Cut or tear off a long strip or chunk of the nori, roll it into a tube shape to help prevent rapid disintegration, then secure it into a veggie or feeding clip and stick it into the tank, positioning it in a low current area.
  • Depending on what type of fish and other inhabitants you are feeding, the clip may be placed either mid-way in the tank, or near the bottom so bottom-dwelling animals like algae eating hermits and crabs can get to it. You may even consider using two clips if you keep both types of tank inhabitants, so they do not have to compete for the same food source.
  • Cut or tear off a long strip or chunk of the nori, roll it into a tube shape to help prevent rapid disintegration, and using a good heavy live or other type of rock or decorative item in the tank, sink and secure the nori on the bottom by sticking a small portion of it underneath the anchoring item. Once the exposed portion of nori has been consumed, lift up the anchor and either let the piece underneath float free in the water, or remove it.
  • Tear or cut off a few small pieces or the nori, hold it in the tank water rubbing it between your fingers lightly to re-hydrate it just enough to soften it up, then release it into the water.
  • Chop or cut it up and mix it into any type of homemade fish food recipe.

If using prepackaged types of nori you can:

  • Just follow the feeding instructions on the package.
  • Add and mix it into any type of homemade fish food recipe.

As a few final notes, in Robert Fenner's FAQs on Foods/Feeding/Nutrition 1 (refer to the "Seaweed For Food" topic), he suggests looking for other types of algae for human consumption like kombu, which he states can also be found in Asian grocery store food departments. Even though nori is very inexpensive and can be messy to deal with, more expensive fares like Seaweed Salads, Selects, Julian Sprung's Sea Veggies and other brands of manufactured algae or seaweed based foods can be purchased readily at fish stores.