FAQs on Duckweeds
Re: Contaminated Tank? Duckweed
Hi Neale, looks like the duckweed took care of it! I read it does wonders for
constipation and I agree! I seen the poop go from mucus white to mucus light
green to normal in less than 24hours!
<Ah, good news!>
Now I just have to figure out how to keep a supply going. I put in a small
breeder box in the tank and plan to let that grow out and then add a little
duckweed at a time to the main tank.
<Should work. Duckweed is/can be a pest. It grows crazy fast!>
I don't want to run a second tank for plants. How do other people keep the
<For most folks, removing Duckweed faster than it grows is the challenge.
Duckweed can be grown on a windowsill though. It is extremely adaptable, even
paper cups will do (standard practical in UK high schools) provided it gets good
sunshine and doesn't get chilled. A large glass bowl, jar or pitcher might be
more practical than paper cups though. Grows outdoors very quickly as well,
though not during cold winters.>
I read so many times that the goldfish out compete the plants. Like it's not
possible to keep the supply of plants in with the fish. In addition, I went by
the local fish store and they discouraged me from having live plants available
as a food source in the tank all the time. The clerk said the water quality
would be bad. You agree?
<Nope. Plants, assuming they're alive, are good for water quality.>
I have the one small fish in 20 gal.
<Sounds like you're doing all the right things. Keep at it! Cheers, Neale.>
Duckweed or Frog bits 4/20/14
I am trying to decide on an easy plant for the aquarium.
<Choosing such is a common problem for many aquarists.>
I have two angelfish, a group of emperor tetras, a few swordfish and a
Bristlenose in the 75 gallon. I had Indian Fern before and bit by bit it
just got sucked up into the filter until it was gone.
I was thinking Duckweed, but I heard angelfish eat them or Frog bits.
<Duckweed won't ever be eliminated by the Angels, and I'd be surprised
if they ate very much of them at all (Angels are more or less entirely
predators in the wild, primarily taking insect larvae). While they might
peck at Lemna spp. while foraging, I'd be surprised if they actually ate
the stuff with much enthusiasm.>
The fish I have may eat the roots of the frog bit.
<Actually less of a problem than you'd expect, assuming the Amazon
Frogbit is growing reasonably briskly. I have kept this species with
herbivorous fish, such as Ameca splendens, which really does eat Frogbit
roots and Indian Fern leaves, and up to a point, the Frogbit in
particular persisted fairly well. Unless the roots are totally eaten
away, it seems to manage okay, and all I did was remove moth-eaten
specimens, leaving the numerous daughter plants to take their place.
None of your fish are anything like as herbivorous as Ameca splendens,
so should be fine. Swordtails are algae eaters to a degree, but they
don't eat (healthy) plants so far as I know.>
I have an empty 10 gallon to maybe keep growing the duckweed in to
replace what is eaten. Just wondering what is the best to get. I like a
floating shade plant.
<Any of the choices you mention is viable. Growing something like Indian
Fern in the spare tank, perhaps on a windowsill, then dumping clumps in
the Angel tank would be a nice idea. Just sometimes it fails to take,
either getting clogged up with blue-green algae or else just going brown
and falling apart, bit by bit. Duckweed is easy to grow, but difficult
remove if you change your mind, and it can be a menace to some types of
filter because it's so small. Strong water currents can submerge
individual plants, pushing them down towards the filter inlet where they
clog the inlet grille. On the other hand, few plants are as authentic as
Duckweed, and in tanks with gentle water currents it adds a nice thick
layer of green, and growing so fast that you can physically remove
nitrate (yay!) on a daily basis if you want. Amazon Frogbit is a lovely
plant, and always worth trying. It looks awesome in tanks that aren't
too deep so the roots (over 20 cm/8 in given the chance) actually anchor
in the sand, creating a really complex habitat that's perfectly suited
to small fish and shrimps.
The only thing it hates is being burned or dried out, but provided your
lights aren't right on top of the water, you should be okay.>
<Duckweed is free, so a no-brainer if you're not too bothered about the
hassle involved in removal. For the other two, trying them out is the
best advice I can give! Cheers, Neale.>
Aquatic Plant Choices
I have discovered the following information about Salvinia.
Four species of Salvinia (S. auriculata, S. biloba, S. herzogii, and S.
molesta) share the feature of egg beater-like hairs. All can be expected
to be aggressive weeds and all four are prohibited as Federal
So that leaves out those Salvinia.
But the species Salvinia natans and Salvinia oblongifolia still seem to
be available. But they require medium lighting. And would likely not do
well in my very lowlight aquarium over the winter.
<Possibly, but if inexpensive worth a shot.>
And sadly Amazonian Frogbit seems to require bright light. It too would
likely not survive in a lowlight aquarium.
<Not found this to be a problem with Amazon Frogbit; have instead found
it adaptable, easy to grow. Yes, does better in bright light, but
doesn't give up the ghost in so-so lighting. Again, inexpensive so worth
Anubis nana might make it, if it can survive a ph of 8-9, low light, and
a not too fussy redcap Oranda goldfish.
<Indeed, an excellent choice.>
But other than that it is small specimens of water lettuce, or java
<Java Moss isn't likely to last long with Goldfish.>
Those are the only two I know will work for sure in my low light
aquarium over winter, and in a pond during the warmer months. Anubis,
java moss, or water lettuce. I am thinking on getting water lettuce.
Which one would you choose? Thank you.
<I'd try them all. Anubias is a no-brainer for virtually all shady
aquaria; the other two are worth a flutter. Cheers, Neale.>
re: Aquatic Plant Choices
Thank you so much Neale! I might give the Amazonian Frogbit a try then.
<If you were local, I'd say "come get some" ... my Panaque's tank is
full of the stuff! Cheers, Neale.>
Snails and Duckweed: FW Snail and Duckweed Control.
Also Plant health. 7/23/2009
First, I can only restate what so many others have said before -
your website is awesome and absolutely my favorite browsing spot.
Thank you again for all your hard work!
<Thank you for the kind words.>
I live in fear of repeating a silly question you have answered a
thousand times before... but I cannot seem to find clear answers
myself. Here goes...
I have a 30gallon planted freshwater tank. Fluorite substrate,
180gph power filter, 96watt Coralife lighting 6700 spectrum, temp
at 78. I live in a hard water area and try to do as little
"messing around" with my water as possible. Ammonia,
nitrites at zero. Nitrates at 15ppm (in local water
unfortunately). Ph 7.7, GH 22, KH 5. I add marine salt to raise
density to about 1.004.
<Sounds great. Thank you for these details.>
Tank residents are 3 Sailfin mollies (1male, 2 females), 4 female
swords, 2 Otos and 2 pygmy Corys (oh, and a random fry if the
swords aren't hungry).
All seem to be doing well.
My problem is with my plants. Most are doing fine. The anarchis
(sp?) grows so fast that I trim it at least weekly. The Ludwigia
looks spectacular and the Bacopa has doubled its original size.
The swords are doing fine though not growing quite as fast - same
for the Val.s.
<Swords need a deep substrate or they get root-bound. You can
try removing the swords, adding some more substrate in that area,
and then replanting if you want them to take off.>
But the Cabomba is horrible! It is dirty grey-green and shreds
apart if I touch it. I am seriously considering just removing it
as I would really love the real-estate to widen the Ludwigia
<Cabombas are touchy at best (I've never had luck with
them) They like very calm water and specific water chemistry. The
salt that you are adding for the Mollies is not likely helping
I also acquired (though I never intentionally ordered or placed)
some floating duckweed. It grows like gangbusters. I like it - it
is pretty and the fish seem to enjoy it. Just one problem - when
the floating plants
hit the current of the filters they get driven underwater. Most
simply resurface a few inches away but some get tangled in...
well in just about everything!
<That sounds like duckweed.>
After a day or two I can easily have duckweed nearly covering
I even find it "trapped" under the edges of the
driftwood log. It is irritating and I worry, of course, about
shading out my other plants. Is there some trick that I don't
know to prevent this?
<Aside from manual removal, not really I'm afraid.>
I do not think I have too much current - there is very little
agitation on the surface. I currently "scoop" duckweed
out of the tank weekly and it seems to make only a small
difference. Anyone want a few handfuls of duckweed? :)
My second question is about the growing cadre of snails in my
tank. At first I diligently removed every one I could find. Then
a brief algae problem convinced me to give them a reprieve. Now,
algae is (praying hard
here) under control and I don't think I "need" the
snails. Apart from appearances, is there any good reason to
<Assuming they are not damaging your plant, I wouldn't
worry too much.>
Do they cause trouble?
<Some species can be destructive to plants, but based upon
your comments, I don't think you are having that
If I just leave them alone, exactly how many of these things will
I eventually have??
<Snails turn waste food into more snails. As the food supply
runs down (algae control) they will breed less frequently. Also,
most snails lay their eggs above the waterline, so you can remove
the eggs when you see
them. You can read here for more information:
Again, thank you so much for your site - I have spent many happy
hours reading and learning!
Tricia in PA
<MikeV in FL>
Re: Snails and Duckweed: FW Snail and Duckweed
Control. Also Plant health. 7/24/2009
Thank you for such a fast reply. If I may, a follow up or
I understand you to have said that there is no other control
mechanism for duckweed other than "scooping and
<It is the only method that is safe for your plants and
Do many aquarists keep duckweed?
<I know a few.>
Would you suggest that I declare war on the duckweed? Or just
keep blowing at it with my turkey baster and scooping out the
excess? Could I even win such a war if declared? :)
<That is a matter of personal preference. If you like how it
looks and are willing to live with it, by all means keep it. If
not, you can win the war by getting as much of it as you can out
every day for a week or so.>
As for the snails, I suspect that they arrived with some live
plants and that their population soared when the algae did. Now
that the tank is clean and clear... will they all die off at once
and foul my water?
<No, they are actually pretty effective when it comes to
resource partitioning, they will just slow their breeding
Will they begin munching on my plants (and with my luck, NOT the
Cabomba that I don't like ...)
<It is a possibility if they completely run out of food, but
that isn't likely to happen.>
Exactly how many snails are too many?
<Hehehe... when you think you have too many.>
Do I redeclare war? Selectively thin? Ignore completely? What is
<If you think you have too many snails, I would selectively
thin, This page:
http://www.wetwebmedia.com/FWsubwebindex/fwsnails.htm has an
excellent method of "herding' them into one place,
making them easy to remove.>
Finally, I am having a hard time identifying the type of snail I
Actually, I know I have a couple of tiny ramshorns. These others
I am not so sure about. Could you look at these (terrible)
<Actually, those pictures are quite nice.>
Anything I need to know about them in particular?
<It looks like you have both Nerite and Trumpet snails. The
first 'in tank' picture is a trumpet snail. In your
second picture, the trumpet snail is the one on the bottom, and
the Nerite is on the top.>
<You can read more about them specifically. here:
And by the way, taking a close up of your tank is a great way to
convince yourself to clean a bit more frequently! Yikes!
<Hehehe, remember, a clean tank is not necessarily a sterile
Again, thanks SO much. My husband swears I spend as much time
reading your website as talking to him! (You DO know considerably
more about fish than he does... he likes his battered and fried
<Heheh, funny, my wife says the same thing about me.>
Thank you in advance.
<My pleasure as always.>
Tricia in PA
<MikeV in FL>