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My water lettuce are dying as seen in this picture:

image.

It is in my pond and I have had around 2 sq meters of lettuce. It was growing rapidly but recently it has developed these symptoms and is dying.

I have added salt to the pond few weeks ago, could that be the cause? Or my filter is making the water move fast?

Ps: Lighting conditions are good.

  • It needs good filtration - its likely the salt, why did you use salt anyway? I take it there are no fish in your pond? – Bamboo Nov 13 '17 at 13:03
  • I forgot to ask where you are in the world and what your temperatures have been like recently, as well as how long have you had this plant in the pond? – Bamboo Nov 13 '17 at 13:09
  • @Bamboo , I ve had this for 3 months, Im in Asia and temperature is around 30C . There are fish in the pond including big fish like arovanas and oscars . I added salt to avoid snails from growing in the pond and its good for fish as well . – new_one Nov 13 '17 at 14:08
  • Arowana is a freshwater fish, so not sure salt's good for it, though immersion in lightly salted water, separate to the main pond, is sometimes used as a treatment for various sicknesses. I reckon its the salt that's affectng the lettuce, unfortunately - your temperatures are well within range for this plant. How much salt, exactly, did you add per litre of water in the pond? – Bamboo Nov 13 '17 at 15:04
  • Looking again at the pictures, looks like there's new growth at the top on some areas that's healthy, so likely its recovering from the salt... don't do it again though! – Bamboo Nov 13 '17 at 19:46
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This is insect damage of some kind the physical evidence for this is overwhelming...notice how certain parts of the leaves look as if a large semi circular mouth has taken a bite what this actually is is the mechanical damage of an insects feeding habits,taking tiny bites all the way across the leaf from edge to edge until the unsupported portion of the leaf falls away.

I could be wrong but it looks as if you’ve more than one type. Other damage looks more indicative of a leaf boring type insect but this could also be diseased plants which can actually be contracted by plant pest insects but my money is on insect damage.

  • Remove all affected foliage
  • rinse each plant thoroughly
  • return to water ...
  • then dose the pond with a fairly liberal amount of fertilizer

Careful though, a fine line exists between a liberal dose to encourage growth in plants struggling back to health and an algae explosion that will be a much bigger problem.

The aquarium salt is not a problem so long as you don’t add any more. It’s not filtered out and can only be decreased by removing a quantity of water and replacing it with fresh. It will eventually dissipate on its on.

Every fish you mentioned will benefit from a small amount of salt in their water. Every now and then it will not harm them in the slightest as long as you follow instructions on labeling to the letter. Check to see what kind of tolerance the water lettuce has and at what specific gravity salt because problematic for the plant. Salt is sodium is on the nutrient list that planst need at least tiny amounts of for total overall health.

I have a 125 gallon soft shell turtle set up with duckweed,frogbit salvinia and water lettuce and it’s is salted regularly and the plants do just fine. I fish out a couple of large nets full every two weeks or so because the growth is unbelievably prolific. Not saying the salt is the cause at all probably turtle poop...and extra fertilizer...but they do excellent even with the salt in the water. It’s barely measurable with a hydra meter if you do it right.

Upon closer examination of your photo a small insect is actually visible in amongst the water lettuce. It looks like an aqua beetle of some kind but maybe just dead terrestrial insect that stumbled into the pond. Sample any and all insects you find in pond to identify them you can incorporate appropriate control measures.

  • I formatted your answer to remove the wall of text look. – kevinsky Apr 30 at 14:31
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I have grown water lettuce. Usually it is exceptionally prolific ( Illegal to deliberately grow it most anywhere in the USA ). I believe it is some kind of bug damage , mine looks very similar but I can't see what is damaging it, so I don't have an answer. Try growing some in an aquarium where you can monitor it closely. I presently have no water movement so that is not the problem.

  • Ok I will try , I put them in a tank and added a parasite killer . Btw in here this lettuce can be found in many swamps and lakes . – new_one Nov 15 '17 at 4:42

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