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I'm thinking of putting some duckweed in my shell dweller tanks to help suck up nitrates and control algae growth.

i thought they'd be good because
1) they're hardy
2) dont take up floor space in the tank
3) they're supposidly great for sucking up nitrates.

i've heard that they can become hard to control and get rid of. but i'm assuming this is only in heavily planted tanks and ponds? being a shellie tank it is quite bare and should be easy to get rid of the duckweed once it gets too much right?

what do you guys think?

It multiplies very fast...in any size aquarium. I don't know much about it, except that I had some magically appear in my 10g (probably came from the plants I ordered) and eventually it almost covered the top of the tank. I slowly started getting rid of it and its almost gone.

Not sure about the nitrates. I just know how fast it multiplies. It may be slower with less light on it...not sure though.

*Kristin*

Hi,
Everything you have heard about duckweed is true.
It will multiply like the dickens, use up nutrients
from the water column, and does float providing excellent
shade for the bottom and hiding places for fry.

Controlling it is not really a problem. Simply decide how
much is enough, and when that amount is reached, take your
fish net, and net out a net full or two or three, whatever
you want. It will grow back in no time, and you simply
repeat the process.

Just don't toss it in a nearby body of water or flush
it down the lines, it is a nuisance plant and will cause
problems if it gets loose in nearby bodies of water.

Frank


-->>> The Confidence of Amateurs, is the Envy of Professionals <<<--

Oops...I washed mine down the sink. I have a septic tank though..so maybe it will be ok. No body of water.

*Kristin*

sumthin_fishy,

All the 3 points you list about Duckweed are true, a hardy, no space (except the whole surface), and nitrate sucking plant.

I have to thin out my layer maybe every other week (high light and CO2 tank). For my situation it can cause problems. If I let it grow too much then there will not be sufficient light in the tank itself.

But it is not a miracle plant that will take care of a significant algae issue for you.

Do you only suspect the algae is from high Nitrates or do you know that for fact?
What kind of algae?

If you do, then how come you have such high Nitrates? Too many fish, too little water changes, or what?

Fighting a problem at the root might be better than trying to eliminate its symptoms.

Hope this helps,

Ingo

---

Proud Member of the New Jersey Aquatic Gardeners Club

I have gone to extreme measures to remove that (words cannot describe what I think about that weed" I will never buy a fish or a plant that has duck weed in the same tank.
Once it gets into your tank it is extremly hard to remove every little bit of it.

Listen to the name it is "Duck WEED"

Have a look in [link=My Profile]http://
www.fishprofiles.com/interactive/forums/profile.asp?userid=6741" style="COLOR: #00FF00[/link] for my tank info

[link=Betta 11Gal Desktop &amp; Placidity 5ft Community Tank Photos]http://photobucket.com/albums/b209/keithgh/Betta%20desktop%20tank/" style="COLOR: #00FF00[/link]

Keith

Near enough is not good enough, therefore good enough is not near enough, and only your best will do.
I VOTE DO YOU if not WHY NOT?
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Hi guys,

thanks for all ur info... and warnings! Keith it sounds like your trying to subliminally hypnotise me into doing drugs!

Do you only suspect the algae is from high Nitrates or do you know that for fact?

nah just suspecting, i do have a test kit somewhere so i'll go check. i just presume nitrates could be a part cause seeing as i have no other plants in the tanks.

What kind of algae?

its a slimey sludgey browny green algae (as u can see i'm very knowledgable when it comes to scientific names!). its just on the glass and it doesnt grow back that fast.

its not overstocked, its a 45G tank with 6 adult multies and fry. and 12G water changes every 2-3 weeks.

it has one fluro which i turn on for about 6 hrs a day. i'll check nitrate levels and get back to you.

from what i gather its easy enough to control, but hard to get rid of for good? isnt it just a matter of scooping it all off the surface? it shouldnt be that hard should it?

i had some but it did not work as the light was to low. It grows very quickly!

You have a cannister yes? I had a horrid time with duckweed when I was running a HOB because it would all get whooshed underwater from the output, get stuck on the intake and rot and clog everything up

If you are going to use it, stick the spraybar underwater.

if i was naughty, i'd suggest salvinia as its easier to deal with, but its a noxious weed, and its probably not a splendid idea to move it around.

Have you considered hornwort? that floats well.

For animals, the entire universe has been neatly divided into things to (a) mate with, (b) eat, (c) run away from, and (d) rocks. - Terry Pratchett

As Calla there stated, hornwort is another good uptaker of nitrates. And also anacharis is another good nitrate absorber. Grows quickly and can be floated or planted in the substrate.

Duck weed has it purposes, and works very well in them. But can get out of control. You will have to thin it out on a weekly or at least every other week basis. As if it becomes overly grown, it will start to die off, thus adding to increased nitrates as well.

The best way to lower nitrate levels is with more water changes. Maybe start doing weekly water changes, vs every 2-3 weeks. I really don't feel this a problem, as it sounds like your tank has a very low bioload. You may just want to invest in to an algae eater of some kind. A BN pleco would be fine in there with the multis, and you would probably never see any more algae at all. If you don't have some kind of an algae eater, you will always get algae growth no matter what. And have to hand remove it. Even with the addition of plants, you will still have algal growth to some extent. You may not see it, as it will be much slower, as it will be competing for nutrients with the other plants, but non the less, you will have it growing.

_____________________________________________________________

There is always a bigger fish...

yes i have a cannister running, a 1200lph one actually so my poor multis get quite a current! i figured duckweed would also help stop the strong current.

k will have a look at hornwort, i just thought duckweed coz we have some in the backyard.

hey Little_Fish nitrates are about 5ppms. is that ok? seems kinda high considering my bioload is quite low. maybe i should increase my water changes.

dunno about adding a BN tho, mayb if i added him b4 the multis it would be ok but now that they have territories are fry i'm sure they would have no problems harassing the BN to death. i've tried snails but whenever the get too close my multis kill them!

Duckweed can be a real pain because each little plantlet is so small. When I had some, it clogged my filter constantly and was a real pain to keep under control, and an even bigger pain to get rid of. If you want a nitrate-sucking floater, go for a salvinia. They are larger and easier to control, and in my opinion, the feathery roots hanging an inch or two into the water is quite pretty. There are even red varieties, but I havn't had much luck keeping them alive for very long.

Hoping that there must be a word for everything I mean...

Here's one reason why one should not toss duckweed into a body of water:


I took this photo a month ago at the Taipei Zoo, Taiwan. Yup, that poor turtle is covered in duckweed too!

Last edited by upikabu at 19-Jan-2006 08:41[/font]

-P

Yup... Duckweed can get REALLY out of control, but IMO it isn't really a problem, you can just scoop it out with a net every now and then...

After about 6 months or so all of mine suddenly died, and I have no idea why... it just all died off. About a year after it all died it suddenly starts coming back for no apperant reason... I've probably got about 10-15 pieces in my 29 right now... not much, but it's a start

Since yer gonna be puttin' it in a cichlid tank, it will probably do more good than harm... the shellies will probably munch on it a bit