# Frogbit and Duckweed - what's up?



## Dustymac (Apr 26, 2008)

No doubt this is one of those questions that I should know the answer to, and will betray my ignorance, but it's been bugging me all week. I have Frogbit and Duckweed in all my NPTs but in two of them, the floating plants are growing completely different.

In NPT #3, the roots are ultra short. The average length for the Frogbit is about 1 1/2". The Duckweed roots are about 1/2" long and very difficult to see.

In NPT #4, the roots are really long. Some of the Frogbit roots are 14" and the Duckweed averages around 2".

So... my question: Do long roots indicate a surplus of some particular nutrient, or do they grow long because a particular nutrient is in short supply and the extra length pulls that nutrient from the water more effectively? 

TIA
Jim


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## helenf (Mar 24, 2008)

I've read somewhere that htey grow long in search of something.

Are the nitrate levels different in the different tanks? Do you reckon you feed more in one tank, compared with the growth, than you feed in the other tank?


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## Diana K (Dec 20, 2007)

Different fish, perhaps nibbling the roots in one tank?


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## HeyPK (Jan 23, 2004)

Plants grow especially long roots when short of nitrogen. This picture of N-deficient Hygrophila polysperma is in the Plant Deficiency Symptoms section of the aquarium pictures:


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## Dustymac (Apr 26, 2008)

Thanks all. I feel a little smarter now!


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## tames (Apr 18, 2008)

What would be the best way to increase the Nitrogen source? Add more fish?


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## dwalstad (Apr 14, 2006)

Dustymac said:


> No doubt this is one of those questions that I should know the answer to, and will betray my ignorance, but it's been bugging me all week. I have Frogbit and Duckweed in all my NPTs but in two of them, the floating plants are growing completely different.
> 
> In NPT #3, the roots are ultra short. The average length for the Frogbit is about 1 1/2". The Duckweed roots are about 1/2" long and very difficult to see.
> 
> ...


Is there any difference in daylength and lighting between the two tanks? My water sprite had short roots (1 inch or less) with 10-12 hr daylength. They didn't look too hot either. I increased daylength to 14 hr. Now plants have long roots and are growing like crazy.

Floating plants do best when we set up "summertime conditions" with long day and warm temperatures. Its a plant hormonal thing and has nothing to do with nutrition.

I tried to upload a photo of my Water Sprite with short roots and paste it to this letter as an attachment file. Its a regular jpg file of 22 KB. If a patient, interested someone wants to try getting it into this thread, just write me at <[email protected]> and I'll send picture.


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## rehdjac (Apr 9, 2008)

My duckweed and American frogbit both have extremely long roots. Thought it was cool at first but it has become a bit unsightly. Each clump of frogbit sends down one long root, most of the rest stay shorter, though not _short_. My tanks are all very under stocked with fish right now.

Can I safely trim that long dangler?


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## Dustymac (Apr 26, 2008)

There is lots of insight in the replies so far. Perhaps I can tie a bit of it together.

Naturally, I should have tested the water for nitrates before posting my message. I did so this morning and the short rooted tank (NPT #3) has between 10 and 50 ppm of nitrates. The long rooted tank (NPT#4) has no perceptible nitrates in the water. Although Diana is correct in that light probably had something to do with the imbalance, it is inverse to her hypothesis. NPT #3 did have lots more light (some direct sunlight) but varietal algae were becoming a problem so I shaded the back of the tank a couple weeks ago.

More importantly, NPT #4 has a much smaller fish load per gallon, and gets much less fish food (aka fertilizer). And when you look closely at the Frogbit and Duckweed leaves in #4, they look more anemic than those in NPT #3 where there are plenty of nitrates in the water. Oddly enough, this is a good thing for me since I added the floating plants to remove nutrients from the water to help minimize algae growth. This has definitely worked in #4.

Another observation: in both tanks the floating plants continue to multiply at about the same rate and the rooted plants in the soil substrate seem to be doing fine under both nitrate levels. Even those pesky dark-veined Amazon Swords! 

Finally, and I may be completely wrong about this, but it seems that pruning the roots does no harm to the Frogbit. I've been doing it liberally because they get tangled in the leaves of the stem plants and start to restrict tank circulation. So far so good.

Thanks again for all the responses!!!
Jim


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## Robert Hudson (Feb 5, 2004)

> American frogbit both have extremely long roots.


If it is american frogbit and not Amazon frogbit, then this is natural for the plant. As a pond plant, its roots will reach all the way to the pond bottom in water that is a foot deep. I have never seen duckweed with roots more than a couple inches long at the most, usually half that.

Adding an extra pinch of fish food that the fish won't eat will raise nitrogen levels, but you want to be very careful doing this.

You may want to go with Amazon frogbit instead, which is a smaller plant more suitable for the aquarium and has shallow roots


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## rehdjac (Apr 9, 2008)

Thanks for the replies. Didn't know that about the American Frogbit. It's the only one my supplier has though, so I'm stuck with it. I snipped some roots in my smaller tanks and it seems to have done no harm.

I just wonder why the plants I received for purchase did not have these long roots if they are natural to the species?


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## Robert Hudson (Feb 5, 2004)

Actually, I was mistaken. Amazon frogbit has pretty long roots as well, but smaller leaves. You probably got young plants that hadn't developed roots yet.


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