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Sea Lettuce turning white


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Nov 30, 2015
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I keep sea lettuce and chaeto in my sump for nitrate reduction. I have a kessil a380 refugium light hanging about 15” from the water surface. The light is on for 10 hours while tank lights are off. I’ve notice the sea lettuce is turning white on the surface of the water. Any lettuce submerged is green and seems to be increasing in mass. I’m I burning the sea lettuce creating more nutrients or is this the color for sea lettuce when it starts to grow. I have noticed some nitrate increase.


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Jun 26, 2020
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I've had a similar issue pop up, but only when the sea lettuce was outside. It only turned white in areas where the sea lettuce was not fully submerged, and an air bubble had built up from the photosynthesis, meaning that the white parts of it were essentially drying out.

Sounds like it's a great time to start harvesting the tops of the sea lettuce, especially if it's at the surface of the sump.

How often do you have some type of algae issue?

  • Constantly Something

    Votes: 241 42.5%
  • Every Month

    Votes: 32 5.6%
  • Every Few Months

    Votes: 68 12.0%
  • A Few Times A Year

    Votes: 82 14.5%
  • Once A Year Or So

    Votes: 59 10.4%
  • Every Few years

    Votes: 29 5.1%
  • Never.....(are you lying?)

    Votes: 36 6.3%
  • Other (please explain)

    Votes: 20 3.5%

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