# Plant growing stop after 2 years in Walstad tank



## Yakuso (Jun 20, 2020)

Hello fellow aquarium friends!

I've started my first Walstad aquarium about 2,5 years ago, with 4-5 cm fertilizer free pond soil under the gravel and easy, fast growing plants. Size is 105x25x16 (42l) and the population 10 neon tetras, with some scampis and snails. 
The first 2 years, the aquarium was absolutely amazing, great plant growth, no algea at all, and I only changed part of the water every 3-4 Months.

But some months ago, suddenly the plants stopped growing! I changed nothing, but suddenly even the Ceratophyllum demersum stopped growing and kind of died, all other plants mainly stayed the way they were, but did not grow anymore either. Finally, after some moths of "frozen" plants with no growing, algea started to build (for the first time!), and now I'm really looking for help, how I can get my plants growing again...

Does anybody have an idea, why my plants suddenly stopped growing even though I changed nothing?
Appreciate any help!

Greetings from Germany

Christopher


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## hoppycalif (Apr 7, 2005)

The obvious answer would be that the soil has run out of some of the needed nutrients, and you don't have enough fish for them to produce enough to take the place of the soil as a source of nutrients. But, often the obvious answer isn't the correct answer! Do you always over feed the fish, so the surplus fish food can provide nutrients?

Welcome to APC! I'm betting some of the more experienced members, including Ms Walstad, a moderator here, will soon give you a better answer.


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## mistergreen (Mar 3, 2007)

Loss of #1 nutrient, CO2 or dissolve Carbon would be my guess. The organics in the soil is used up.


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## aquabillpers (Apr 13, 2006)

My 29 gallon Walstad tank has been running for more than 10 years without a change in the substrate. The plants are the descendants of the original plants. There has never been anything added to that tank except water and fish food. 

It's not a case of the original substrate running out of nutrients. I've read (Diana Walstad) that takes place around 6 months.

The source of all plant nutrients after 6 months is fish food in one form or another. Do you have enough fish?

Has your water chemistry changied, either from the source or because evaporated water has been replaced, gradually hardening the water?

Are your lights wearing out? That happens with some lighting types.

I appreciate your frustration. Keep working at this problem and you will fix it.

Bill


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## Yakuso (Jun 20, 2020)

Thank you for all your fast an helpful answers!

The fish&feeding thing is a good hint, because some (5) of my fish died over time due to the neon illness. Fortunately the current population is constant, no more losses. But because of that I feed less now, due to the smaller population. Maybe I've cut the feeding too much! I will start to feed more! I would also like to get some more fish again, but right now I don't want to go to the store because of the c-virus..

I've also added some of this basic FE-mineral-fertilizer: https://www.amazon.co.uk/Tetra-PlantaMin-Monthly-Fertiliser-Aquarium/dp/B002X02YN6
I've forgot to mention, that my upper plants used to turn red when near the surface, and no they do not anymore since the growth stop.

Since I have a LED Light Tube, light wear out shouldn't be a problem? Or do these LEDs also wear out?

As far as CO2 is concerned; is this something that is stored also within the soil? Because I never added CO2 manually to this tank and I'd really prefer not to do, if possible, since one of the reasons I've started the Walstad tank was to have a low-tech tank with easy maintenance.


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## hoppycalif (Apr 7, 2005)

Yakuso said:


> .....
> Since I have a LED Light Tube, light wear out shouldn't be a problem? Or do these LEDs also wear out?
> 
> As far as CO2 is concerned; is this something that is stored also within the soil? Because I never added CO2 manually to this tank and I'd really prefer not to do, if possible, since one of the reasons I've started the Walstad tank was to have a low-tech tank with easy maintenance.


All forms of light fixtures can change with time - nothing works forever. I haven't tried to find out if my LED lights lose intensity with time, but I also haven't used one for more than a year or so.

The El Natural method relies on the breakdown of the organic matter in the soil to provide CO2. It doesn't produce a large amount of CO2, but with the lower light intensity and easy to grow plants that this method uses, there is no need for a lot of CO2, just a continuing supply of it. It would be an interesting experiment to keep a record of the CO2 level in the water every week or so for a few years to see how much it changes with time. Ms Walstad may have done this and might have some data for us.


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## aquabillpers (Apr 13, 2006)

CO2 is in short supply iin a Walstad tank. Some will come from a new soli substrate and - maybe - from a mature one. Other sources ae the atmosphere and animal respiration. Water disturbance drives it out, so filters and the like should be used with care, if at all.

Ms. Walstad has suggested adding excess fish food to the tank and letting it sit on the bottom for the plants. 

It's quite possible to grow plants in an old Walstad tank without adding anything but fish food. My only problem is that I have to prune too often. 

If you haven't read Walstad's "Ecology of the Planted Aquarium", you might. It has a wealth of information on NPT's. There is also a forum here at APC, El Natural, that is devoted to that subject.

You've kept that kind of tank long enough to show that you know what you're doing. Keep at it.

Bill


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## aquabillpers (Apr 13, 2006)

hoppycalif said:


> . . .The El Natural method relies on the breakdown of the organic matter in the soil to provide CO2. . . . .


A question: I know that the organics in a new soil substrate generate CO2 (and other nutrients) for about 6 months, but after that the only source of plant nutrients is fish food, delivered to the substrate via fish droppings.

I've wondered if that produced CO2 as it decomposed, or if maybe its decomposition liberated carbon to be taken up by the plants through the toots. Do you have any further thoughts om that? Thanks.

Bill


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## ukamikazu (Jun 4, 2010)

aquabillpers said:


> A question: I know that the organics in a new soil substrate generate CO2 (and other nutrients) for about 6 months, but after that the only source of plant nutrients is fish food, delivered to the substrate via fish droppings.
> 
> I've wondered if that produced CO2 as it decomposed, or if maybe its decomposition liberated carbon to be taken up by the plants through the toots. Do you have any further thoughts om that? Thanks.
> 
> Bill


Not to step on Hoppy's toes, but I'd look into BOD and COD, or biological oxygen demand and chemical oxygen demand.

Decomposition only occurs if you have a nutrient source, be it a corpse, excess food or mulm, oxygen and water. We've got the water part down and plants or really turbulent flow can provide the oxygen so now all we need is food in the form of excess fish food and mulm. Little bacteria do their work and provide CO2. It's all connected. As Hoppy and you also stated, fish also provide CO2 and ammonia to keep your biological filter going which also provides some CO2, generally speaking and grossly oversimplifying if I'm being honest.

This can get complicated because it is all a balancing act that can easily go wrong. Find the balance. A few more fish, a little bit of excess food and some nice, strong but gentle laminar flow and you'll almost be there. And plants. An excess of correctly lit plants.

Yakuso, you're on the right track and in the right place with Hoopy, aquabillpers, Michael and our Diana. You'll be in good hands. Good luck to you and don't hesitate to reach out!


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## hoppycalif (Apr 7, 2005)

aquabillpers said:


> A question: I know that the organics in a new soil substrate generate CO2 (and other nutrients) for about 6 months, but after that the only source of plant nutrients is fish food, delivered to the substrate via fish droppings.
> 
> I've wondered if that produced CO2 as it decomposed, or if maybe its decomposition liberated carbon to be taken up by the plants through the toots. Do you have any further thoughts om that? Thanks.
> 
> Bill


I'm a bit over my head in this discussion, but I have to believe that if there was as form of carbon, other than CO2, available to our plants someone like Seachem would have synthesized it and would be selling it as liquid carbon. (Excel is not a natural substance.) As I understand it, CO2 is the only natural form of carbon available to plants, whether aquatic or terrestrial. And, as I understand from Diana's book, the substrate with dirt in it is constantly producing CO2, primarily from bacteria, as I recall. But, a healthy growing El Natural tank cannot maintain enough CO2 in the water for much more than 4 hours, so she recommends a split lights-on day, 4 hours or so on, with a 2 hours or longer siesta for the CO2 in the water to build up again, and another 4 hours or so with the lights on again. She measured the CO2 in the water and had the data to show this actually works well.


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## Michael (Jul 20, 2010)

Some aquatic plants can also obtain carbon from bicarbonate, thus the desirability of alkaline water with enough hardness to supply it. And there are four other strategies to increase carbon availability. See _Ecology of the Planted Aquarium_, pp. 96-101.

Many people know I hate acronyms, but I'm going to suggest one: EOPA for _Ecology of the Planted Aquarium_.


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## terryna (Mar 16, 2018)

mistergreen said:


> Loss of #1 nutrient, CO2 or dissolve Carbon would be my guess. The organics in the soil is used up.


very nice


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## Yakuso (Jun 20, 2020)

Thank you very much for all your helpful and encouraging answers!

I will change the light setup aswell. Then I'll wait to see if my changes (light, feeding, more fish) work, and if not, I'm thinking about adding some CO2.

PS: Yes, I've read EOPA, I really like it, it's my "manual" for this tank


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