# Lighting intensity and duration with the Walstad method



## PK1 (Oct 4, 2005)

There is no shortage of discussions on this topic on the web, but there seems to be differences of opinion: D. Walstad herself recommends high light levels for relatively long duration daily (south facing window), whereas many others argue that more light = algae problems, which is very intuitive to me given my experience with high-tech methods. Unless one can manage CO2 effectively, which is difficult at high light levels, algae problems are almost inevitable. 

I have setup my first low-tech tank as follows:

- 4 gallon Eheim Aquastyle tank with its standard LED light and filter
- the light intensity seems too high visually, I'll measure PAR levels today and will post results back
- substrate is 1" of MGOC mixed with Eco-Complete, plus a 1" cap of Eco-Complete for a total of 2". I soaked and rinsed the Miracle Grow a few times during the course of a week, and then spread it out to dry once, so it is not fully mineralized. I then mixed with Eco-Complete at a ratio of 4:3 dirt:Eco-complete for the bottom layer
- plants are Rotala Indica, Ludwigia Repens, Crypt Undulata, a half-dead Amazon Compacta bought from my local Pet Smart and a few pieces of Frogbit

I am debating as to what my light duration should be, and whether or not I should reduce the intensity by putting a layer is something between the light and the water - PAR measurements will help for this discussion, to follow. 

I'd appreciate any thoughts on the above. 

On an unrelated topic, my water was slightly hazy when I first setup the tank yesterday (filled up half way, planted, drained and refilled VERY slowly using a Tom pump), but this morning the water is still hazy. Should I let it be for now or change again? On the same topic, how frequently should I change the water in the beginning while the rank is establishing?

Thanks for all the help as I begin the El Natural journey!


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## PK1 (Oct 4, 2005)

Alright, here are the PAR readings:

- 250 µmol m-2 s-1 at the water surface, the light is about 3" above the surface level, this is as high as it will go, I can't raise it any higher
- in the 50-55 µmol range at the substrate, which is about 8" below the surface
- there is very little difference with the glass cover on

My thoughts were to keep the PAR level around 40 at the surface to avoid algae issues, but I welcome suggestions.


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## Michael (Jul 20, 2010)

Thanks for posting your PAR levels, this makes it possible to make meaningful suggestions.

Walstad does not advocate high light. She does suggest some natural light as a supplement to artificial light for overall medium or moderate lighting. But frankly, the lighting section of her book has become outdated with the rapid changes in lighting technology and the availability of PAR meters.

Most of the low tech or Walstad tanks we have measured with our club PAR meter have about 30-40 umol at the substrate. So your tank is a little higher than typical. You could compensate for this by shorter photoperiod and/or use of the siesta schedule. Most of my tanks are in the 30-40 range, and are on a schedule of 5 hours on, 3 hours off, 5 hours on. The purpose of the siesta schedule is to allow CO2 levels to rebound during the siesta.

Walstad's recommendation of some natural light tends to mimic the actual light conditions in nature. In the morning and afternoon, sunlight strikes the surface of the water at an acute angle. Much of the light is reflected from the surface and does not penetrate the water column. Near noon when the sun is highest in the sky, less light is lost to surface reflection and light levels below the surface are much greater. So the light available to plants is low to medium for most of the photoperiod, with an intense but brief exposure at midday. This can be measured in a garden pond. So some people have adopted a midday burst schedule. This is a feature of the ADA method.

The short answer is that you have light levels that are a little higher than typical for a Walstad tank, but you can manage this with photoperiod length, schedule, and perhaps a little shading from floating plants.

The hazy water will probably go away on its own, but you can do a water change if it bothers you. MGOC is famous for releasing large amounts of tannins into the water, coloring it brown but clear. This can go on for months. Water changes will eventually take care of it. Some people use carbon filters or other chemical filtration to deal with it.


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## PK1 (Oct 4, 2005)

Thanks Michael, this is very helpful. I put a sheet of parchment paper on the glass lid and this brought the PAR level down to 30 at the substrate, so I am at the low end of the range you recommended. I was also planning on having a photo-period of 7 hours, but with lower PAR ratings I'll extend it to 10 hours with a 3-hour siesta as you recommended. I'll see how it goes for a while and adjust as needed, my only concern it that given that most of my plants were ordered via the internet (I don't have a good lfs), they are not in the best of shape, so I am hoping the lower PAR levels won't slow their recovery down or contribute to their demise - we'll see. If my frogbit takes off, I can eventually get rid of the parchment paper and keep enough of it to keep PAR levels in check.

The hazy water doesn't bother me, I just want to ensure it doesn't cause problems. How often should I change the water in the first few weeks?


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## Michael (Jul 20, 2010)

Frequency of water changes depends on how soon you want to put fish in the tank. With your soil, you are likely to have unsafe (for fish) levels of nitrogen compounds for up to a month. Healthy plants will use these as nutrients, and speed the "cycle". You can just let this run its course without water changes.

If you want to put fish in sooner, you will need to test the water and do water changes to keep ammonia etc. at safe levels. Chemical filtration will also help during this period, but will be unnecessary afterward.


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## PK1 (Oct 4, 2005)

Thanks. I am in no rush to put fish in the tank right now, I can simply let the tank run its course. I am only asking because I frequently came across recommendations to do regular water changes for the first couple of months and slowly back off when the tank is established.

If no water change is needed, I am not insisting on it . I'll take the wait and see approach.


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