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Duckweed index question.

sciencefiction

sciencefiction

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26 Feb 2013
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I was hoping Darrel is around as well as that's kind of his method.
Basically I have a low tech soil tank. The journal is on the following link: The "Disaster" | UK Aquatic Plant Society

The tank is setup since mid April and is doing well. The plants are growing somewhat lush and there's no algae that I can see at all, no stunted or damaged plants. However, I've noticed for a good while my floating salvinia minima isn't in great shape. In fact it wasn't doing as good soon after the very start. The tank has never been dosed with anything yet. It's just grows pale and small. Besides that it still multiplies fast. I never had luck with floaters in my other tanks either and they eventually died despite not getting any algae or issues with the rest of the plants.

So the question is what should I dose with this tank now? This is a total low tech so far not dosed with anything. I also have tropical plants emersed like calathea and peace lilys which show no deficiencies that I can see.

Here are a few pictures below of how it always looked/looks:

This one is about 3 weeks after setup. You can see some of the new leaves growing paler than the initial ones already.

dscf4661g.jpg




This one is two months after setup. Almost all have gone pale now and some browning but that could be because they got caught under water.
dscf5109c.jpg



And this is from 3 months after setup, salvinia still growing fast. I remove handfuls of it daily but not looking great.
m9v1.jpg



And from today 4 months after
1br3.jpg


Now the rest of the plants for that period of time have really grown lots and well. I'll just post a couple of shots to give you an idea but it's all in my journal.

From this state below taken two weeks after setup. Most of the plants initially melted and one can't even see on the picture I've got vallis or aponogeton crispus or stem plants like ludwiga, mexican oak leaf, bacopa which I had to start over from just some couple of melted stalks each.
dscf4637s.jpg



To this 4 months later(last night) I managed to propagate a lot of them. There are no deficiencies that I can see. So what is the salvinia telling me?
vztg.jpg


And my other emersed plants are looking fine and have grown lots:
oekz.jpg


8iee.jpg
 
Ha, ha. Thanks.
Any pointers to my duckweed question?:) I am thinking of dumping the salvinia and replacing with another floater that possibly shows deficiencies better. I've been reading salvinia just likes tons of nutritients in the water to be green. Otherwise it grows paler/brownish and if no nutritients are available, stops multiplying and the root systems grow longer, which isn't the result in my case.Plus it's a low tech so I'll never have tons of nutritients in the water. It's basically the only plant that's "suffering" in there. Even the moss, java fern and anubias are growing well and they aren't rooted to the soil substrate either.
 
Think you might have answerd your own question (not loads of nutrients) most of the good stuff is in the soil for the roots and the stuff on the top may just be getting the left overs. Ceg is the man to ask but im sure he is going to say its lack of nutriants
 
Yes, it's lack of nutritients in the water column is probably the case. Last time I checked, if the test is anything to go by, the nitrates were barely registering at 5ppm, but that's normal for that type of tank. The point is that the emersed tropical plants, java fern, anubias and moss aren't showing nutritient deficiencies, well not yet anyway.
 
Maybe the light is to bright for them? in the way some plants when sun burnt go red to deal with excess light, but this might go lighter or become waxy? or less green could be magnesium deficiency i think...
 
Thanks Nutty, I don't know about the light amount. It's quite a distance from the plants but the LEDs can be powerful.
I never dosed magnesium in tanks because my water is rather hard 12dGh but I also have dolomite in the substrate which contains magnesium, just not sure if that gets released to the water column at all. I've always had issue with floaters, including my other tanks so it's something tight to the water that I don't dose normally and it could be magnesium I guess. I really need to get some Epsom salts or something and try it out.
 
Hi scifi,
perhaps this is a light/fert imbalance. The floaters have access to unlimited co2, and the most light too being floaters, so nutrients are the most likely cause as the plant will be trying to grow FAST. However, it seems to be reproducing consistently so maybe this is just how its settled with what it has available. If it has slowed reproduction down too then it will definitely be a nutrient deficiency.
It could also be down to plant mass. Over time everything has grown considerably and maybe its just got to the point that fish waste/water changes isnt providing fundamental amounts of fertilisers for the faster growing floaters, with the issue worsening as more growth occurs? The other plants may be doing well as they grow slower and do not need the amounts, plus they are shaded by the floaters reducing their demand....but im sure thats the point of the duckweed index, to highlight deficiencies so you can act before the rest suffer. (dont know about the other emersed growth, but again they may be slower growing so less effected than the floaters)
You could try adding a small amount of an all in one fert to see if there is an improvement.
Im sure Darrel will have a complete answer for you, there is some advice here which may help, perhaps try some nitrate and magnesium:
Duckweed index ferts advice | UK Aquatic Plant Society
TBH it doesnt look like a nutrient deficient tank, the floater is still reproducing so maybe its just paler as its nearer the light.
Cheerio,
Ady
 
Thanks Ady. I think you are right. Yes, the floaters are reproducing still and they are possibly faster growers than anything else in the tank and get the most light too. I can't see other deficiency in the tank but maybe they'll appear eventually and my floaters are ringing the bell I can't hear :)
How much concentration as in ppm should I aim at from the macro nutritients as a start dose I wonder?...like a weekly dose...

I know I'll be crusified for that question here(ferts and algae relationship), but since this is a low tech with limited co2 and if I trigger faster plant growth via the ferts is there any chance I may cause a co2 shortage and possibly algae? That's the only thing kind of bugging me now. The tank has been super clean so far.
 
Hi mate....sorry that I have not read every word on your thread & not really studied the question but if those terrestrial plants have their roots in the water then I have worked out (not a difficult equation really lol) they just sap up ferts like you would not believe!!
I have to double dose EI with my tank due to the immersed plants!
 
Foxfish has a point. Since you have a dirted substrate you may not notice the stems plants etc have any problems in terms of nutrient problems. But since the floaters rely on column ferts only they may be out competed by the immersed plants.
 
Yes, that makes sense Foxfish M.W. Thanks guys. I'll dose some macros first and see. The nitrAte according to the one time I tested was barely registering 5ppm if those tests are accurate. Should I just start with one weekly dose and at what strenght? I am also guessing that whatever isn't used the soil/clay substrate and the hydroton pebbles may just store up for later use?

Also, I am not doing much water changes(1 every 3 weeks or so) so not sure how that will affect the tank.
 
When I consulted Darrel regarding my amazon frogbit he suggested added KNO3 at 5ppm and after a week if theres no greening response use "Epsom Salt" to add 5ppm of Mg and you should get some response. He commented that its not important to add the exact amount so I guess you could experiment with the dosing so long as your fish won't get harmed. And as a last resort add a total mix of nutrients and he suggested to me this APF Plant Nutrition in Bottles (dry) - APF Complete - Fertilisers I'm guess any all in one ferts will be fine.
 
Thanks Michael. I'll put a dose of KNO3 and a bit of P. I am going to have to buy Epsom Salts. As I mentioned, the substrate has dolomite which is supposed to slowly release calcium and magnesium without affecting the hardness, but maybe it's way too slow :)Should the existing ones get greener or the new growth only? Sorry for the stupid question but I never took notion of that.
 
Hi all,
Sorry for the delay in replying, but I've been away for a few days, and not had WWW access.
sciencefiction said:
Thanks Ady. I think you are right. Yes, the floaters are reproducing still and they are possibly faster growers than anything else in the tank and get the most light too. I can't see other deficiency in the tank but maybe they'll appear eventually and my floaters are ringing the bell I can't hear
Click to expand...
The first thing I'd say is not to worry, everything looks fine. The fact the Salvinia and other plants are growing shows that they aren't suffering from any major problems.
Michael W said:
When I consulted Darrel regarding my amazon frogbit he suggested added KNO3 at 5ppm and after a week if theres no greening response use "Epsom Salt" to add 5ppm of Mg and you should get some response. He commented that its not important to add the exact amount so I guess you could experiment with the dosing so long as your fish won't get harmed. And as a last resort add a total mix of nutrients and he suggested to me this APF Plant Nutrition in Bottles (dry) - APF Complete - Fertilisers I'm guess any all in one ferts will be fine.
Click to expand...
If you want greener and faster growth I'd still pretty much go with Michael's comment.

Salvinia is quite interesting as it does show a lot of differing morphological response to varying light and fertiliser regimes. I find mine tend to go paler in the summer, presumably because they are receiving more ambient light, and producing either and/or;
  1. less chlorophyll,
  2. or more anthocyanins.
In the first case this is because it doesn't need any more chlorophyll to harvest the available PAR, in the second case the pigments are acting as a "sun-screen", to stop the damage from Clive's "photon torpedo" of excess non-utilisable light <plants have started going brown help please! | Page 3 | UK Aquatic Plant Society>.

These are a couple Salvinia plants, that I picked up from the tanks at the back of the lab this morning and scanned. The tanks are in a N. facing window and both pretty low nutrient, but the small plant came from a tank with a lid and low lighting, and the larger plant from an open-topped tank which gets a lot of ambient day-light.

Although they look like different species, the original plants all looked like the small version.
Salvinia_sizes_zps4c94ada0.jpg


I'll pick some up that have been outside in the pond, and I'll predict that they should be a lot bigger, and probably a lot browner.

cheers Darrel
 
Thanks for the reply Darrel. The tank is not getting even minimum ambient light becuase it's in the corridor of an apartment and there are no windows in there. We don't have to use the top light for the most part because when we are home I've set the tank lights to come on instead. :) So no light besides the photoperiod but maybe the LEDS are a bit too much for them.
The difference of salvinia on your picture is exactly the same as when I setup two bowls on the window sill with salvinia, one dosed with ferts, one undosed. The only thing is the dosed bowl got tickly covered in green algae but the plants grew way better. I maybe did quite an overdose of ferts though.

Unfortunately, the tank is leaking from one side so I have to deal with that first to see if I am going to have a tank or a pool at home :)
 
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