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  1. Duckweed
    by (matthew.kaufman) (19 Mar 92)
  2. [F] duck weed lowered nitrates
    by (Doug Knowles) (Tue, 18 Jan 1994)
  3. [F] Bioload, nitrate levels, Apistogramma
    by (Mark Armstrong soft) (Fri, 4 Mar 1994)
  4. Aquatic Plants Digest V2 #222
    by Andrew Boyd <> (Sat, 28 Sep 1996)
  5. Aphids gone!
    by "Darren J. Hanson" <djhanson/> (Sun, 14 Dec 1997)
  6. Ivy duckweed for aquascaping?
    by eworobe/CC.UManitoba.CA (Sun, 5 Apr 1998)
  7. Amazon Frogbit?
    by krombhol/ (Paul Krombholz) (Thu, 30 Mar 2000)
  8. RE: Wolffia
    by "James Purchase" <jpurch/> (Tue, 8 Aug 2000)
  9. (No Title)
    by ()


by (matthew.kaufman)
Date: 19 Mar 92

In article <> (Ben Cushman) writes:
>      Is there anything I can do to get rid of duckweed without hurting  
>my other plants, including some floating watersprite? 

Net it out. Do this every day or so for a few weeks. Throw it away or
feed it to something that will definitely eat it (my common goldfish
never did but goldfish are purported to eat it. Note they will eat most
other green things.) I feed it to my earthworm cultures.
>      Further, is there any way to prevent duckweed growth in the  
Global thermonuclear war? Dry out the earth's surface?

It's just a pest that comes in as contaminants with plants and sometimes
in fish water. I have it in almost every tank except those that I've
been relentless about cleaning it from. It's not completely useless -it
does consume some metabolites and if you let it make a thick cover over
the surface of a tank many fish like the shelter (of course, your submersed
plants may not like the lack of light that results...) Shyer fish
like killies and apistos actually seem happier with a thick growth of
floating plants, and it is THE easiest floating plant to grow, and most
prolific, no contest.
>                              Thank you-
>                              Ben Cushman
>                              Reed College

Ahh... but can you not | Copyright 1992 Permission for
also make bridges      | reproduction in printed media or by pay-for-read
out of stone?          | services explicitly disallowed. Permission granted
                       | for reproduction by USENET and like free facilities.

[F] duck weed lowered nitrates

by (Doug Knowles)
Date: Tue, 18 Jan 1994

I have gleaned several good bits of help from this group, 
so here is my contribution.

I have a 29 gallon freshwater tank that has been going for about 
18 months with 1 large angel, 1 6" pl*co, 1 large gouramie,
2 dwarf gouramies, 2 swordtails and 2 platies.  UGF with 2 powerheads,
plastic plants, some algae controlled by pl*co and occasional glass 
scraping.  20% water changes twice a month with gravel vacuuming.  
Lighting: one plain old PlenPlax fluorescent. (20-40 watts?)

After loosing 2 dwarf gouramies, I checked the ammonia (0) and 
nitrates (> 150 ppm!) Started twice weekly 20% water changes and 
reduced feeding.  This brought nitrates down to 40-50 ppm, where they 
stayed fairly constant after several weeks.  Maintenance resumed at 
about 3 times a month.  

I wasn't very happy with this level of nitrates, so I decided I needed 
something to eat the fertilizer.  I bought a couple of scoops of 
duckweed, performed daily rinses and complete water changes for a week
in a quarantine bucket with shop light, then dumped it in the aquarium.

Nitrates are now constant at less than 5 ppm (detection limit of 
Aquarium Pharmaceuticals dry tab tester.)  I harvest about half 
the duckweed during each maintenance.  It pretty much covers the 
surface by the next time.

Simple, easy. Happy fish, happy aquarist.

[F] Bioload, nitrate levels, Apistogramma

by (Mark Armstrong soft)
Date: Fri, 4 Mar 1994

In article <> (W. Keith Newsom-Stewart) writes:
>I am trying duckweed in a heavily planted and well lit 70 gallon tank.
>I will slowly add fish and monitor Nitrate to see what happens.  I have
>about 3/4 of the top covered with duckweed and Salvinia.  

If you are using a sump, how about putting the duckweed there? It would
require another light and a large sump. It seems that the duckweed would
block the light to the tank, but in a sump it wouldn't matter. If you
are using a Wet/Dry filter, the sump should mainly contain nitrate and
very little nitrites and ammonia forcing the duckweed to convert the nitrites.

Mark Armstrong

Aquatic Plants Digest V2 #222

by Andrew Boyd <>
Date: Sat, 28 Sep 1996

In APD #222, Eric Deese wrote:

>Can anyone suggest a method of eradicating duckweed? It thrives in my
>tanks far too well. I routinely remove a layer off the surface of the
>water with my weekly water changes. Are there any fish (or other creatures)
>that are natural predators, that won't do too much damage to my other
>tank occupants, bith plants and fish?
>Eric Deese   Columbus, Ohio  USA

Howdy Eric!  Australian/New Guinean Rainbowfishes (Melanotaenidae) love
eating Duckweed! IMHO some (the larger species like M. trifasciata) are more
efficient than others (smaller species like M. praecox). 

Aphids gone!

by "Darren J. Hanson" <djhanson/>
Date: Sun, 14 Dec 1997

At 03:48 PM 12/4/97 -0500, Aquatic Plants Digest wrote:
>Aquatic Plants Digest   Thursday, December 4 1997   Volume 02 : Number 1117
>Date: Thu, 4 Dec 1997 14:51:02 -0500
>From: "Merrill Cohen" <>
>Subject: Re: Aphids gone!
>I found an easy solution ( dumb luck) by placing a small power head  to
>move the surface of the water.  The Aphids evidentally didn't like this
>enviroment and they are gone.  Give it a try and post your results.  I have
>lots of surface plants, like Hydrocotyle varieties, Ludwigia
>helminthorrhiza, Phyllanthus fluitans, and two varieties of Duckweek --
>they are now clean of Aphids and don't mind being moved around continually
>by the power head moving the surface.

I'm trying to get caught up on some back issues of the digest and somebody
has probably already mentioned this, but duckweed doesn't like to be pushed
around a lot by wind or water currents. In fact, this seems to be the only
reliable way to get rid of it once it has established itself in a tank short
of tearing the tank down and bleaching everything. Create enough current to
push it all to one side and instead of watching the patch steadily grow to
take over your tank choking out everything beneath it, it will slowly shrink
and die off.

- -- dj

Ivy duckweed for aquascaping?

by eworobe/CC.UManitoba.CA
Date: Sun, 5 Apr 1998
Newsgroup: rec.aquaria.freshwater.plants

Lemana trisulca is a submerged aquatic plant and therefore you dont need 
any special tricks to keep it under the water.


Amazon Frogbit?

by krombhol/ (Paul Krombholz)
Date: Thu, 30 Mar 2000

>From: Connelley Barton <>
>Subject: Amazon Frogbit?
>I've noticed in recent discussions, the mention of Frogbit.  I believe
>that Chuck Gadd indicated that it was a good indicator for iron
>deficiency.  I'm trying to locate some.  Westerleigh Aquar., in N.Y.,
>lists Giant Duckweed(Lema Polyrhiza) for sale.  Would this possibly be
>the same thing?

Spirodela polyrhiza is the name, and it is definitely not frogbit.  It is
just a duckweed that gets a little larger than some of the other duckweed
species.  It often gets a purple color under the leaves.  Frogbit is genus
Limnobium.  It is floating and has leaves an inch or two in size with
petioles of an inch or so.

Paul Krombholz, in Central Mississippi, with more rain on the way, and my
car with a flat tire.  (Meaning it isn't going to be nice doing the 20 mile
round trip commute on a bicyclein the rain, tomorrow)

RE: Wolffia

by "James Purchase" <jpurch/>
Date: Tue, 8 Aug 2000

Sephen Boulet asked about Wolffia (not Wolfia).

(No Title)


"The third family of the Arales, Lemnaceae, has six genera, which are
cosmopolitan, occurring in fresh water throughout the world. The floating or
submerged plants have little economic importance but serve to some extent as
food for waterfowl and fish. Some (especially duckweed; Lemna minor) are
used extensively in physiological and genetic research, where the small size
is a great advantage."

"The Lemnaceae, with 6 genera and 30 species of minute floating aquatic
forms, is widespread in the temperate and tropic zones. The family is
remarkable for the smallest known flowering plants, the duckweeds (Lemna
species) and watermeals (Wolffia species). Certain of these green, leaflike,
flattened species, with or without rootlets and only a few millimetres
across, are used in aquariums and pools as ornamentals or as food for
waterfowl and fish."

"Flowers, rarely produced, bear only the essential organs, no sepals or
petals: the male flower has one or two stamens and the female a single
pistil. The plants reproduce primarily by basal division."

For a key to the Genus Wolffia, go to

also look at (, especially for

While I guess that you might find someone who sells it, I'd suggest that you
might go look for some where you live..... here in Toronto, I have found
Wolffia in several bodies of water in the middle of the city, so its far
from rare.

I don't think I'd recommend letting it anywhere near a display tank - it
grows and multiplies every bit as fast as the regular Duckweeds and can
become a right royal pain in the butt to get rid of, but it might be fine as
a fish food, as it really IS much smaller than Duckweed (which is already
pretty tiny).

James Purchase

P.S. - if you can't find it locally, let me know, and I'll mail you a
container of it.

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