The Lighting Requirements for Chaetomorpha

Written by jody paterson
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The Lighting Requirements for Chaetomorpha
(aquarium fish 4 image by cherie from

Chaetomorpha is a seaweed popularly used in aquariums to provide refuge for small fish. It can tolerate a variety of light levels, but does best when the mass of strands that make up this "spaghetti algae" are routinely turned so that all parts of the plant are regularly exposed to the light source.


The word "algae" conjures up the green slime that accumulates on your aquarium walls despite your best efforts to get rid of it. But Chaetomorpha is a macroalgae, or seaweed, that aquarium enthusiasts deliberately select for their tanks. All those thin strands that make up Chaetomorpha create an excellent hiding place for fish. The seaweed is also fast-growing, adaptable and effective at converting waste nitrogen compounds into plant nutrients.

Light levels

Chaetomorpha grows well in any level of light. For optimum growth of a macroalgae, however, you'll want to provide a minimum of one watt of light per litre of aquarium water, presuming a depth of no more than 30 centimetres. So if you've got a 60-litre tank, you'll want a light source that provides at least 60 watts.

The Lighting Requirements for Chaetomorpha
(Sunshine image by Luke Haverkamp from

More light, less shedding

The one drawback of Chaetomorpha is its tendency to shed small strands, which can clog up the intake and lead to floods. To prevent this problem, trim the plant regularly and shake its dense ball of fibres loose to expose more of the plant to light.

Spores and light

Preventing the reproduction of macroalgaes is a subject of interest within the aquarium community, and light levels could turn out to play a role in that. Some aquarium keepers light their tanks 24 hours to prevent macroalgae from forming the spores the plants use to reproduce. While those who use this method report that it's effective, there isn't enough comparative information from those using different lighting periods to be able to confirm 24-hour lighting as the optimum strategy.

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