# Duckweed vs. Water Lettuce



## Rusalka

Since these two plants have decided they cannot coexist I was wondering if anyone can weigh in on which one they think is better and why? Which is better at ammonia uptake and removing other impurities? Which is easier to maintain in a planted aquarium? Which looks better? Which a better oxygenator? 

Does anyone have any other favourite floating plants?


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## dwalstad

Rusalka said:


> Since these two plants have decided they cannot coexist I was wondering if anyone can weigh in on which one they think is better and why? Which is better at ammonia uptake and removing other impurities? Which is easier to maintain in a planted aquarium? Which looks better? Which a better oxygenator?
> 
> Does anyone have any other favourite floating plants?


For the same amount of growth (biomass increase), one plant species would be expected to remove about the same amount of nitrogen and other impurities. I would choose the more vigorous grower in your situation and/or the one you like the most.

BTW, floating plants don't oxygenate the water. Only submerged plants oxygenate the water.


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## Rusalka

That make total sense re: floating plants not being water oxygenators. They are "air" photosynthesizers - I'm sure there's a scientific term I'm missing out on here. haha!

So what you're saying is 30 grams of duckweed will do the same job as 30 grams of water lettuce. The only difference is 30 grams of duckweed might cover 50% of my tank surface area, and 30 grams of water lettuce may only be one plant. Do I have that right? 

Is water lettuce generally as prolific as duckweed?


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## Rusalka

Or is it that which ever one grows fastest and proliferates more will do a better job? More plant growth = more detoxification?


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## cs_gardener

Rusalka said:


> Does anyone have any other favourite floating plants?


My favorite floater is frogbit (Limnobium laevigatum). It's large enough to be easy to scoop out of the tank, grows quickly, has thick leaves that can withstand some current (it's good at resisting being tossed under by the current), and I like the look of the long roots floating around.

I also like red-root floater (Phyllanthus fluitans) because it has such a great color, is also large enough to be managed easily, and grows quickly when it's happy. It is more delicate than the frogbit and can get knocked around by the current. It doesn't do well for me when I use a glass cover over the tank unless there's a good deal of air space and air circulation.

I also have Salvinia minima and it is a decent floater. It multiplies very quickly and is many times larger than duckweed so it is easier to manage, though not as easy as the frogbit or red-root. It tends to need decent airflow and is easily knocked under water by the current since it has a much a smaller size than the frogbit or red-root.

I've managed to get rid of duckweed out of all my tanks except one. I find it to be a true nuisance and I became very tired of having green bits stuck on my arms after any tank maintenance even after rinsing them off (BTW I'm female and not particularly hairy). It's such a pain trying to scoop out the excess since I had to net it and then it stuck to the net (and my hands, and the bucket, and anything else it comes into contact with).

I never had much luck with water lettuce. I had it for 6 months or so and it grew well and then it gradually dwindled and died off, I'm not sure why. After it failed I tried the frogbit, red-root floater, and Salvinia and they've been growing well for me for years now. I regularly dump handfuls of them in my compost pile.

Oh, I also have Ceratopteris pteroides which can get very large (12+ inches across and 6 inches above the water surface with roots that can get over 6 inches long and form a mass about 4 inches in diameter). It takes a while (think in terms of months) to grow that large but is only suitable for larger tanks. It doesn't seem to grow particularly fast unless it has a lot of light. And it's VERY good at blocking light to the rest of the tank.


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## dwalstad

Rusalka said:


> Or is it that which ever one grows fastest and proliferates more will do a better job? More plant growth = more detoxification?


Yes.


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## cfreeman

I agree with Catherine on the Duckweed. It is a nuisance and it has taken a lot of consistent effort for me to eliminate it from my tanks (it hitchiked in on some other plants).

Water lettuce has worked well for me, it seems to be a heavy feeder and removes a lot of nutrients from the water column. It helped me get new tanks established without suffering major algae outbreaks. The advantage of this plant, and the others mentioned by Catherine is that it is easy to manage and remove from the aquarium. You can easily thin it out to manage the % of cover it provides between your light and the water. I also like the look of the roots hanging in the water.


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## Dustymac

I'm not disagreeing with anyone about Duckweed - it is a mess. I like it because it's roots are short and don't get hung up in the vals or stem plants, limiting water circulation. Although it's hard to get rid of, you can get it out of a tank as long as you aren't trying to grow other floaters at the same time.

I prune mine with a serving spoon instead of a net - easier to rinse them off in the sink. And you can limit their spread in the tank with a strip of wood floating on the surface. 2" x 1/2" seems an ideal size cut about 1/16" shorter than the front-to-back depth of your tank as measured on the sides. (Tanks usually bow outward in the middle) If you need to get down and dirty working in the bottom of your tank, just slip in the wood strip and sweep the Duckweed to one end of the tank, then hold it in place with a suction cup until you're done.

Hope this helps,
Jim


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## helenf

If you happen to have goldfish or similar in another tank, growing duckweed on the tanks you can is great, because you can feed it to the goldfish. It's wonderful food for them - very nutritious. 

I am now growing as much duckweed as I can on my NPTs and feeding it all to the goldfish. They love it, I love it, we all love the duckweed. (Agreed it can easily get everywhere if you're not careful, though).


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## cs_gardener

Dustymac said:


> I'm not disagreeing with anyone about Duckweed - it is a mess. I like it because it's roots are short and don't get hung up in the vals or stem plants, limiting water circulation. Although it's hard to get rid of, you can get it out of a tank as long as you aren't trying to grow other floaters at the same time.
> 
> I prune mine with a serving spoon instead of a net - easier to rinse them off in the sink. And you can limit their spread in the tank with a strip of wood floating on the surface. 2" x 1/2" seems an ideal size cut about 1/16" shorter than the front-to-back depth of your tank as measured on the sides. (Tanks usually bow outward in the middle) If you need to get down and dirty working in the bottom of your tank, just slip in the wood strip and sweep the Duckweed to one end of the tank, then hold it in place with a suction cup until you're done.
> 
> Hope this helps,
> Jim


The spoon sounds like a good idea for scooping duckweed, I'll have to try that in my virtually no maintenance shrimp tank where I haven't bothered waging war against it yet. My problem is I DO grow other floaters and the darn duckweed gets under/on them and wont come off (I've had to scrape it off the bottom of red-root floater with my fingernails). I also have plants like Cyperus helferi, Cryptocoryne spiralis and Val nana that have lovely long leaves that float along the water surface. They'd get in my way when trying to remove the duckweed, end up with the ends getting pulled out of the tank covered with duckweed, splashing water and duckweed everywhere (yeesh, it's been months since the last battle and I can feel my blood pressure rising) and it was just a horrid mess. I decided duckweed was just not compatible with my efforts to have a relaxing hobby.  And to think that when I first got it I thought it was no big deal.


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## 01krisp10

Weird, I had water lettuce and duckweed growing together in peace for months and months, wonder what the difference was?

Duckweed is annoying, I've just gotten used to the idea that once a week I'm bound to go walking around town with duckweed stuck in my hair and on the back of my short sleeves that I didn't notice I dipped into it. 

I have it in all my tanks, not so much because I enjoy it, but because it does its job and I don't have the patience to fight it all that much. Thanks for the wood block and spoon tips, great ideas!


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