# Allelopathy - Cabomba vs duckweed



## filedor.com (Jun 2, 2012)

I read the Diana Walstad Method book and I'm impressed. But I have a problem now, I know I can't grow duckweed having cabombas. I did the mistake to place 8 cabombas (all of them already started to root) in a 20 gal tank, and I also have Elodeas, 1 Anubia (doing great perfectly green), 1 mini java fern, and some duckweed (not sure what type is it, each leaf around 1 cm and it has some dark nerve-looking lines on top). My duckweeds were inhibited and some of them started to turn yellow. I already removed all cabombas and I placed them in my Quarantine tank.

I know Diana Walstad doesn't mention anything about refugiums. So my question is: Can I have a refugium with only duckweeds, java moss and java fern and in my main tank have my Elodeas + Eleocharis acicularis + Hemianthus Callitrichoides + anubias? I know Eleocharis inhibits duckweed but only 10% and also, it will help to inhibit the Hemianthus (dwarf baby tears) from emerging (I heard sometimes they would un-root then float, is it true?).

Please help me with this question, I would really love to have some duckweeds in a separate tank (Refugium), can I do this? Can I still use the water I had with the cabombas? I want to keep my copepods alive, do I need to change all the water and cycle once again? *are the cabomba's allelochemicals going to disappear just by removing all the cambombas*? 

I have 1.5 garden soil, and 1.2 silica sand, already 1 month since the first time got cycled, fern + anubias are green and thriving, elodeas are "ok" but not doing so good... cabombas were beautiful green and all rooted (I already removed them). I have lots of copepods and lots of red ramshorns, and probably around 8 MTS. No algae growth. No fishes inside of the main tank yet. Refugium not ready yet... I'm waiting for this answer. Temp 87 F. No CO2 injection. Zero ammonia & nitrites, and around 2ppm nitrates, PH 74. 8-[


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## DerekFF (Nov 21, 2011)

Duckweed is a floater, how was it inhibited? If anything it would be the last to die

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## Skizhx (Oct 12, 2010)

Personally, I've never heard any credible cases of allelopathy causing problems in aquariums. I would consider other factors, first. The fact that you say your duckweed normally has dark green veins, and say it started yellowing, suggests to me that it's something else contributing to the poor health of your duckweed.

Walstad does discuss allelopathy briefly, but also doesn't place much real emphasis on it as an important factor, except a few cases which were attributed to algae, and which she concluded due mostly to lack of other explanations.

Otherwise, if it is a case of allelopathy, I would treat it the same way as any toxin in the water. If it's in the same water system, it will be distributed throughout, and will persist after the source is removed until it's absorbed, removed, or neutralized.

Best of luck!

(Just to be clear, I'm not saying allelopathy doesn't exist, I'm just saying I've never seen a real case where the solution to someone's plant troubles stemmed from allelopathy. If there was, I'm sure there would be an "incompatible plants" sticky somewhere on every planted aquarium community)


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## filedor.com (Jun 2, 2012)

Skizhx said:


> Walstad does discuss allelopathy briefly, but also doesn't place much real emphasis on it as an important factor, except a few cases which were attributed to algae, and which she concluded due mostly to lack of other explanations.
> 
> Otherwise, if it is a case of allelopathy, I would treat it the same way as any toxin in the water. If it's in the same water system, it will be distributed throughout, and will persist after the source is removed until it's absorbed, removed, or neutralized.


Thanks a lot for your answer. Well, actually I started to doubt it is duckweed. The dark veins on top were there since I bought the 3 of them. It started to turn all yellow, and after being almost dead I removed them and placed it here with some plants that I know are always combined with duckweeds (usually in nano shrimp tanks) like you can see in this picture I have some Pogostemon helferi, Hemianthus Callitrichoides, an a few lemma minor. 








I didn't try putting Lemma minor in the main tank with Cabombas, so idk if it will have the same result, but as far as I can see, probably I exagerating by placing so many big Cabombas just because they looked so nice (Cabomba "Silver-Green") and because it's not the typical Cabomba (I have been living in Korea for 2 years, and I discovered I can buy many odd plants for a lil price  )

I couldn't find anywhere in Diana Walstad's book talking about how to neutralize the water containing X type of Allelochemical, any ideas how to remove Cabomba's allelochemical before I install my (what I call...) Diana Walstad's Refugium version? 
Here's my refugium design for a 16 gal tank:


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## DerekFF (Nov 21, 2011)

Oh no thats not duckweed lol. If you had duckweed you would be scooping a mat of it off the surface every week. Looks like frogbit or maybe dwarf water lettuce. Duckweed is about 1/100th the size of those floaters there

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## Skizhx (Oct 12, 2010)

That is definitely not duckweed. The leaf looks like frogbit to me...

Magnesium deficiency is generally characterized by the veins of the plant standing out darker. Of course someone will come along and explain why this is the one case and plant where I'm totally wrong (such seems to be my luck). I'll admit, I've never seen that. How are your other plants doing? Any holes in the leaves? Yellowing? Other problems?









Frogbit









Duckweed

At least we can certainly agree that allelopathy against duckweed is not the issue 

As far as neutralizing such chemicals, I have no idea how you would go about that, if it's even a possible solution. Never known an issue of allelopathy to actually prevent anyone from keeping two plants together successfully, and as such, have never seen a solution or procedure to handle such a problem.


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## digital_gods (Apr 23, 2010)

You said that you just bought the duck weed. I found out a month ago that frog bit can be challenging to ship because it will go bad quickly. I shipped a large mass of it bundled with other plants with the entire contents wrapped in wet paper towels. It was in transit less than 24 hrs and it didn't make it. Maybe you are possibly experiencing something similar. 

Regards, 

Robert


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## filedor.com (Jun 2, 2012)

Skizhx said:


> That is definitely not duckweed. The leaf looks like frogbit to me...
> 
> Magnesium deficiency is generally characterized by the veins of the plant standing out darker. Of course someone will come along and explain why this is the one case and plant where I'm totally wrong (such seems to be my luck). I'll admit, I've never seen that. How are your other plants doing? Any holes in the leaves? Yellowing? Other problems?


Thank you all so much for your answers, I'm really grateful. Yes, now that you all mention, it really seems some sort of frogbit, and for sure its not water lettuce, and its not a duckweed (now I can realize about that). At the beginning I thought it was duckweed pholyrriza. The good thing is, any other plant has been affected, they are doing nice, no holes on the plants, no yellow color. The only exception is my Lysimachia Nummularia Aurea in my main tank, which is doing fine but I can see that the new leaves are growing pretty small, but I read in the plantpedia saying:
" 'Aurea' form are excellent indicator plants for NO3, showing very full, robust leaves with bright coloration only when its nitrate needs (>5 ppm) are met. Its growth is often stunted or slowed when these nutrients are deficient."
My main tank has no fishes, but has around 15 MTS and prolly more than 50 ramshorn snails, and its filled with copepods and has a nice tanning, I feed my tank with fish food everyday and after 2 months and I still get 0 ammonia 0 nitrites 0 nitrates, no water changes, just topping with water as Diana Walstad mentioned (yeap... 2 months without fishes, I'm still trying to get my whole "scaping + refugium" idea clear and well studied, before I bring fishes from my QT into my main tank  ) . I have 3 nice pieces of driftwood, my PH is always 72. I use API liquids.

I moved all my Cabombas to my QT, and I plan to remove Elodeas because as Diana Walstad mentioned "they inhibit daphnia". I already have a huge amount of copepods.

Any of you guys have any experience combining Diana Walstad + refugium? I know she doesnt mentions it, but I wanna try to put some plants which I don't think can fit in my main tank, such as my Echinodorus Kleiner Bar (too big for my 20gal main tank) and also I wanna have my main aquarium duckweed (lemma minor) free, therefore I will have those in my refugium as I drew in my design. Any advices?


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## Skizhx (Oct 12, 2010)

The only problem I can see with a refugium would be if the plumbing causes any surface agitation.

As Walstad has stated on these forums, she eliminates surface agitation so the CO2 that accumulates from organic decomposition wont be lost.

Otherwise, I have to be honest in saying that I don't see much point. If it were me and my money, I would just buy a larger tank instead of setting up plumbing to circulate water through a two separate tanks (the refugium and the 'show' tank), since the benefits would be exactly the same (more plants to act as filters, larger water volume to dillute waste, etc), and would be much simpler to setup and maintain, with less room for error or equipment failure.


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## filedor.com (Jun 2, 2012)

Skizhx said:


> The only problem I can see with a refugium would be if the plumbing causes any surface agitation.
> 
> As Walstad has stated on these forums, she eliminates surface agitation so the CO2 that accumulates from organic decomposition wont be lost.
> 
> Otherwise, I have to be honest in saying that I don't see much point. If it were me and my money, I would just buy a larger tank instead of setting up plumbing to circulate water through a two separate tanks (the refugium and the 'show' tank), since the benefits would be exactly the same (more plants to act as filters, larger water volume to dillute waste, etc), and would be much simpler to setup and maintain, with less room for error or equipment failure.


Sorry I took much time to answer, but in fact I didnt finish reading the book... so I was eating the whole book (from page 81 to the end). Now I understand what you are saying is true, but now I have a new question based in two sections from the book:
1. I will quote Diana Walstad talking about CO2 in the aquarium:
"If the hobbyist uses natural means (e.g. decomposition) to provide CO2, it is especially important to limit CO2 loss from the aquarium. CO2, because it is a gas, will be lost by all measures that increase air-water mixing, such as vigorous agitation of the water by spray bars, airstones, and 'wet-dry' filters. The hobbyist must balance water movement that enhances nutrient uptake by plants, distributes heat, and brings oxygen to fish without driving off all the CO2. Thus, I try to keep water agitation just sufficient for providing the fish with oxygen."
2. She also talks about "Guidelines in Aquarium Keeping" saying:
"Filters and water movement - Moderate water movement from filters bring nutrients to plants, oxygenates the water for both fish and bacteria, and distributes heat. But intense filtration (trickle filters, multiple filters in one tank) is unnecessary and may be detrimental in a well-planted tank. I use hang-on-the-bank' filters for tanks of 29 gal or less. For tanks longer than 30 inches, I use canister filters, because they efficiently (and quietly) move water from one end of the tank to the other.
To reduce tank maintenance (as well as promote plant growth), I remove the finner filtering media from the canister filters. That way I don't have to clean the filters as often and there is less chance that the filters will cause problems should they malfunction."
She talks about having a canister without the filter media, that's why I will just use a refugium instead of a canister, also because that way I can put the heater out from my main tank, and also put a huge java fern (that works like miracle) in this refugium instead, because this fern it's way too big. I will probably do the same with my Echinodorus (put it in my refugium) since I read around the internet saying this plant's roots will go all over the substrate and the leaves might cover much of the light, thus the need of a bigger tank. Besides that, this plant is excellent because it is an emergent plant and will also have beautiful flowers ^_^. What do you suggest? Echinodorus in my main tank or refugium? (I bought it yesterday without any tags so I'm not sure what kind of Echinodorus is, but grown leaves are 8cm wide, 25cm length, young leaves has a red-green hue, and the flowers come along with some small leaves&#8230; see the picture)








The small 10 gal fish tank in the background is my bare bottom QT.

*MY QUESTION:* So obviously I can see that water agitation or air-water mixing, if it is more than moderate water movement will for sure make a CO2 loss. But in the other hand, it seems to me, she didn't say we should eliminate the water agitation. So my big question (and please please help me) is:
_If we need a moderate water movement to bring nutrients to plants, oxygenate the water for fish and bacteria, and distribute heat, what does she means by "moderate water movement" and how much would be enough? ok so, no spray bar, but then a tube dropping water on one side of the tank? (or both?) and what would be the distance away from the surface?_


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