My fish stay at the bottom.

[adavisus]

Yup, water lettuce is noticed to have less raphides in softer water. Question is, how toxic the levels. At high levels, asphixiation is likely when the gut, throat, windpipe all swells up...

 

[Faebinder]

In other words... agree to do lilies before Adavisus and Meyer start duking it out with swords.

 

[adavisus]

Raphides are a significant hazard. Something to be wary of. When water lettuce mass up, you might think oh, its a good grower. That has more to do with the fact that it is viciously toxic to grazing critters...

Like, yew tree seeds, gobble it fast and pft.... dead

As a means to shade fish, ummm, a mass of water lettuce may be problematic

 

[Meyer Jordan]

Yup, water lettuce is noticed to have less raphides in softer water. Question is, how toxic the levels. At high levels, asphixiation is likely when the gut, throat, windpipe all swells up...

Yes, these physiological reactions are a sign of high levels of ingestion of Raphides in Mammals!. There is no scientific data to support that the ingestion of raphides is harmful to fish. There are anecdotal opinions scttered bout the internet but even most of these state that there is no real proof of toxicity. Many substances, at high or massive levels, Will prove to be toxic.

 

[adavisus]

Calcium oxylate is insoluble in water, it would affect the soft tissues of fish and reptiles just like glass splinters would. You will find mentioned herbivores, plant grazers generally are mentioned as being at risk

You will also notice problems with fish, tadpoles, on ponds where water lettuce rots off in volume. Not good stuff to be floating about, tiny splinters

If you have thirty ponds, and water lettuce rotting off in a couple or three, you would notice. I sure notice the skinny tadpoles that never get to maturity

"Raphides seem to be a defense mechanism against plant predators,[6] as they are likely to tear and harm the soft tissues of the throat or esophagus of a plant predator chewing on the plant's leaves.[7][8] The venomous process is in two stages: mechanical pricking and injection of harmful protease. Typically ingestion of plants containing raphides, like those common in certain houseplants, can cause immediate numbing followed shortly by painful edema, vesicle formation and dysphagia accompanied by painful stinging and burning to the mouth and throat with symptoms occurring for up to two weeks"

You might also look up what kidney stones are made of. Oh, science mentions calcium oxylate, quite a bit, making quite a few references to, don't guzzle the stuff...

oh and as for the protease inhibitors ingested, now there you are really moving into the realms beyond scientific knowledge as far as biological weapons are concerned

 

[Meyer Jordan]

plant grazers generally are mentioned as being at risk

Again, these are mammals.

"Raphides seem to be a defense mechanism against plant predators,[6] as they are likely to tear and harm the soft tissues of the throat or esophagus of a plant predator chewing on the plant's leaves.[7][8] The venomous process is in two stages: mechanical pricking and injection of harmful protease. Typically ingestion of plants containing raphides, like those common in certain houseplants, can cause immediate numbing followed shortly by painful edema, vesicle formation and dysphagia accompanied by painful stinging and burning to the mouth and throat with symptoms occurring for up to two weeks"

What is the source of this quote?

Still all anecdotal, no hard scientific data.

I did find this-
"They provide habitat and protection for a number of insects that associate with the plant but they appear to have few insects that feed on them. The main predators appears to be herbivorous fish, (particularly carp), snails, flatworms and ducks, other birds may also feed on duckweeds but reports are few in the literature. The musk rat appears to enjoy duckweeds and the author suggests that many other animals may occasionally take duckweeds such as pigs and ruminants."
DUCKWEED World Watch
http://www.fao.org/ag/againfo/resources/documents/DW/Dw2.htm

 

[adavisus]

wikipedia.Where you have a quote like that its fairly easy to find its origin by putting one sentence into google

Yes, it is science fact, water lettuce is specified as being a hazard to plant grazers, herbivores

Hazard to soft tissues, protease (nasty can of worms that, scientifically speaking)

Fish graze plants

 

[adavisus]

Here's some can of worms, seeing as 'american science' is shall we say, rudimentary to non existent, you have to go to other cultures when finding out stuff. Folk in Korea are very impressive at phyto filtration, Indians are rather good at nutrition issues

"Aquatic weeds are one of the major unconventional feed ingredients tested for aquafeed formulation. Tannin content in the water lettuce, Pistia, has been quantified (26.67 mg g(-1); dry weight) and graded levels of which (12.5-200 μg) have been incorporated in the reaction mixtures to evaluate any change in the in vitro activity of the principal digestive enzymes from the three Indian major carps (IMC), namely rohu (Labeo rohita), catla (Catla catla) and mrigala (Cirrhinus mrigala). Result of the experiment revealed that the Pistia tannin (PT) significantly inhibit/lower the activities of the digestive enzymes from three IMCs in a dose-dependent manner, even at very low concentration. Significant variation in the reduction of the enzyme activities was noticed between the three fish species, as well as between the three enzymes studied. Among the three species studied, digestive enzymes from L. rohita were found to be the most sensitive to the PT, whereas enzymes from C. catla were found to be comparatively least affected. On the other hand, protease and lipase activities were comparatively more affected than the amylase activity. The results of the study suggest that more stress should be given on the elimination of tannin while incorporating feed ingredients of plant origin in fish diets."

Well golly gosh, I have to go a long way to find out what I already know from my own back garden

 

[Meyer Jordan]

Here's some can of worms, seeing as 'american science' is shall we say, rudimentary to non existent, you have to go to other cultures when finding out stuff. Folk in Korea are very impressive at phyto filtration, Indians are rather good at nutrition issues

"Aquatic weeds are one of the major unconventional feed ingredients tested for aquafeed formulation. Tannin content in the water lettuce, Pistia, has been quantified (26.67 mg g(-1); dry weight) and graded levels of which (12.5-200 μg) have been incorporated in the reaction mixtures to evaluate any change in the in vitro activity of the principal digestive enzymes from the three Indian major carps (IMC), namely rohu (Labeo rohita), catla (Catla catla) and mrigala (Cirrhinus mrigala). Result of the experiment revealed that the Pistia tannin (PT) significantly inhibit/lower the activities of the digestive enzymes from three IMCs in a dose-dependent manner, even at very low concentration. Significant variation in the reduction of the enzyme activities was noticed between the three fish species, as well as between the three enzymes studied. Among the three species studied, digestive enzymes from L. rohita were found to be the most sensitive to the PT, whereas enzymes from C. catla were found to be comparatively least affected. On the other hand, protease and lipase activities were comparatively more affected than the amylase activity. The results of the study suggest that more stress should be given on the elimination of tannin while incorporating feed ingredients of plant origin in fish diets."

Well golly gosh, I have to go a long way to find out what I already know from my own back garden

What is the title and authors (or link) of the document that this quote is from?

I find it interesting that tannins are the subject of the quote. No mention is made of raphides, which is what started this discussion. Even so, it was not inferred that any toxicity was involved, but only suppression of enzyme activity. This can be found in every day foods of the human diet.

 

[adavisus]

The hazard of calcium oxalate is well known. What else is in the sap....

http://search.proquest.com/openview...a8ecd14/1.pdf?pq-origsite=gscholar&cbl=326330

The venomous process is in two stages: mechanical pricking and injection of harmful protease

Good luck with that, you are on your own figuring that biologic weapon

 

[Meyer Jordan]

The hazard of calcium oxalate is well known. What else is in the sap....

http://search.proquest.com/openview...a8ecd14/1.pdf?pq-origsite=gscholar&cbl=326330

The venomous process is in two stages: mechanical pricking and injection of harmful protease

Good luck with that, you are on your own figuring that biologic weapon

As previously stated, the key word here is "inhibit". The work toxic or any other variation of the word does not appear in this entire paper
Within the main body of the linked paper is this-
"Previous study by Mandal and Ghosh (2009a) depicted tannin concentration in some natural and potential fish food items/ingredients of plant origin that ranged between 5.38 (coconut oil cake) to 34.3 (phytoplankton) mg g-1 dry weight. Result of the present study revealed tannin concentration as high as 26.67 mg g-1 in the Pistia leaf meal."
https://scholar.google.com/scholar?...ved=0ahUKEwjr0ebKp8HSAhWM4SYKHepoDYYQgQMIGDAA
(click on PDF academia.eu on right side of page)
Phytoplankton, a regular and natural part of the diet of any omnivorous or herbivorous fish, contains 28% more tannin than Pistia, yet fish somehow manage to thrive. Toxic, apparently not.
As to the hazard of calcium oxalate being well known. It has been shown that as applies to humans and other mammals, yes. As applies to fish, no scientific proof of this has been presented so far and very little anecdotal.

 

[adavisus]

Really not interested in specious disputes over well defined words

 

[CindyA]

I like duckweed but it never lives long in my pond and it gets into the filter... Water lettuce attracts lotsa insects and seems always beaten up in my pond.

Hyacinths and lily pads are the best experience but lily pads will be stable in the center of your pond if you toss the pot in the center.

Think I better go with lily pads! lol Will lily pads grow tall enough in 3 feet of water if I put it in the center (deepest part) of pond?

 

[adavisus]

Medium size waterlilies like a two foot depth, set on a one foot deep tub, a 3' depth is poifect

Hardy waterlilies are a lot tougher than tropical waterlilies, which are especially vulnerable in spring to fish grazing, the very delicate early foliage is a very tasty nutritious snack when they start up

This can catch out folk early summer, ravenous fish outnumbering tasty salad munchies