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Salvinia Molesta


Bender
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I bought home a bag of 'duckweed' last week from the lfs and found that along with duckweed and azola it contained a lot of a plant I couldn't identify. After much searching I found it is a juvenile form of a fern called salvinia molesta. It has oval leaves attached along horizontal stem and floats very nicely on top of the tank, with hairy roots hanging below. The leaves are covered with fine hairs that trap air and keep it floating, and if you look at them with a magnifying glass they look like a field of little egg beaters! The problem is that it is an environmental menace. It is a class 2 pest Australia wide, which makes it illegal to sell, and land owners are expected to eradicate it from water bodies on their property.

One of the best references I found it this pdf from Weeds of National Significance there is a picture on page five that shows all the growth stages. The little clump of leaves at the right is the stage I have, and the one your most likely to come across in 'duckweed'.

I don't think any of us would be stupid enough to empty our tanks where it could get into our water ways, but not every one is as smart, so by not buying or growing it and letting others know we can help keep our native fishy's safe!

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Personally I wonder if some of these scientists are that smart???....Please don't misinterpret this post as saying it's Good to introduce exotic weeds to local waterways....but

These"weeds" are very Good at extracting nutrients from water.....and are actually used in some countries to purify waste water

Why they go berserk is generally because the waterways are FULL of nutrients from farming process.....

Humans stuff with the environment so much.....it's hard to know what's worse.....water course heavy with nutrients that wash out to sea.....

or weeds that clean it up along the way.

I suggest controlled areas of water weed to clean water courses.....then

Regularly harvest these control areas for stock feed would be smart idea!

Take out nutrients and put them back on the land!

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:) It would seam the intelligent thing to make use of the 'nuisance' properties of such plants for by using them to soak up the mess we add to the system and use them as stock feed or better yet process them for fish-farm foods. I would love to have the capital to set up such a self contained system. Surely the amount of carbon they would absorb from the air should also be considered as beneficial in a farming context!

Unfortunately government is rarely into supporting the intelligent thing, and industry is often dead set against it. Unchecked as they currently are, these plants really do major damage downstream, some simply by blocking the water flow and removing natural habitat for the native fauna, others like the water lettuce providing major breeding grounds for mosquitoes. Although, now you mention it, those same nutrient rich waters they purify is irrefutably damaging. It is catch 22.

I would hate however for carelessness of the aquarium trade to be responsible for introducing new changes in any of our remaining natural habitats, so would personally like to avoid supporting the sale of such weeds.

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Salvinia is quite common among hobbyists still. Some people find it really useful in their tanks as a great surface cover. I'm not sure if the whole genus is noxious, but I would think so.

The problem with using plants like this in our waterways is how easily they can get out of control. If we could solve that, then they would be a great nutrient absorber. They also fix nitrogen.

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I let the lfs know yesterday afternoon, the lady has been really good there and I'd hate for her to cop a fine. It seams their wholesaler has been supplying it as 'giant' duckweed. At least if you have it and know what it is you can make good use of it in your aquarium while taking care not to spread it. But with all the rain and flooding we've had, I hate to think of all the ponds with "giant duckweed" that will be overflowing into local waterways.

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LINKS TO NSW DPI (This will vary from state to state :) )

Non-saleable weeds: http://www.dpi.nsw.gov.au/agriculture/pest...CZhbGw9MQ%3D%3D

Salvinia restrictions by NSW region: http://www.dpi.nsw.gov.au/agriculture/pest...amp;weed_id=118

Weeds of National Significance (WONS) listing for Salvinia: http://www.weeds.gov.au/cgi-bin/weeddetail...?taxon_id=13665

Duckweed is not listed in non-saleable or on the noxious weeds page, and isn't showing up on the national searches, so I think you are safe there :)

As far as I can tell, the salvinia listing only applies to S. molesta, so other species within the genus should be fine (though don't take my word for it!) If these exist in the country or not, I do not know.

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Think I may not have been as clear as I should have! Duckweed is not considered a problem, so they can sell that. This is Giant Duckweed It looks just like the normal stuff, only a bit bigger. It is banned for sale in some USA states, but I haven't found anything to indicate it's a problem here.

What my lfs has been selling as 'giant duckweed' was actually salvinia molesta. It's got hairy leaves and roots, quite easy to distinguish from duckweed, once you know. It's quite possible that the wholesalers have everyone confused!

EDIT: just realised I've rambled on to no purpose whatsoever! Please excuse me, it's been 36 hours since i slept, and I'm waiting for a washing machine repair guy to show up so I can go to bed!

Edited by Bender
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Bender, you were quite clear, it was Canfeleq's post I was replying to, as I think you saw. Sleep deprivation is fun! Who needs drugs...

Thanks Callatya for actually bothering to find the relevant documents, unlike me :)

Nothing new, but I find it worrying that lfs give out wrong info or sell to customers, in cases that could result in fines and other serious penalties for those customers.

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