Zapins

Out of curiosity what is the PAR value at noon on a sunny day?

Michael

See post number 8. Noon in June in Dallas: 1,700 umols.

Zapins

Wow, and what would you consider high light for aquatic plants? I know there seems to be some debate on this topic, but roughly?

BriDroid

How accurate is that 1700 Michael? The Apogee sensors are calibrated for either natural sunlight or electric light from the factory. I'm assuming the clubs meter is for electric light? If so, I wonder how far off it would read under natural light?

Michael

Zapins, that is what we are all trying to figure out! Here's my subjective opinion, and I am inviting scorn from all corners with this. But I can take it, LOL! All numbers refer to PAR at substrate.

20 umols is low, below this only the most shade tolerant plants will grow well. 40 umols is medium--a very large variety of plants will grow well. 80 umols is high and will grow almost anything. Much above 80 umols at the substrate you are driving the Ferrari on an icy mountain road, and had better know what you are doing.

Something I think is important is photoperiod, and how long the light is at what intensity. Again, my subjective opinion is that the "midday burst" schedule most closely resembles nature, and you may be able to flirt with high PAR using that method. This comes partly from my observations of sunlight in my own ponds. Except at midday, surface reflection greatly reduces the amount of light received by submerged plants.

BriDroid, our meter has both electric light and sunlight settings. The outdoor readings were taken with the meter in sunlight mode. However, the manual says that if you use the wrong setting the error is only 5-10%, I can't remember up or down. You can get that much change just by moving the sensor a fraction of an inch in a planted tank, so I regard it as insignificant.

Zapins

Interesting. Those values fall roughly into the same value difference I see between hydroponics values and aquatic plant values. It seems like aquatic plants need between 10-20x (closer to 10x) less nutrients than hydroponically grown plants. So it doesn't surprise me that from 1700 to 80 PAR makes sense, that is roughly 20x less light, which is inline with 10-20x less nutrient requirements. Obviously light drives the entire process, so if you need 20x less light you should need roughly 20x less nutrients on average.

niko

Michael is right - PAR of 50 is all you need. Everything above that puts you in a situation where you need to raise the CO2 and run all day after nutrients. Most people will say that works but it really does not because there are interactions between the basic fertilizers that happen when the CO2 is to high. These interactions are not what we normally discuss (like P and Fe for example). Basically you can be starving the plants from ferts that you assume you have enough of because you add a lot of them (K is one example).

Once again ADA seems to have figured all of that out more than a decade ago - pH=6.8 and medium light. Providing most of the nutrients through the substrate can be seen as a stable way to provide them. If you rely on ferts floating free in the water who knows what happens when you over or underdo this or that other factor. That's where we have been swimming for the last decade.

High PAR can be provided in many ways but you better understand what happens if you actually provide it. It looks like the experiment that the club started 3 or so years ago have given numbers that start to make more sense now. Another experiment that I hope will materialize is finding what is a "proper" COD (organics loosely put). JeffyFunk is trying to find that out. Once again - ADA has had their eye on that too and even sells a seemingly toylike test kit for it. I am glad that we are talking about all these things, despite the funny time stretch from the "Amano Revolution" in the late 90's until now.

Zapins

While Amanos setups do seem to match some of the ideal values we are discovering I am not convinced they knew about these values first and then designed their products to match. I think they just happened upon a formula that seemed to work and stuck with it.

niko

Checked the PAR of two common bulbs - a parabolic one used to light up the driveway and a kind of bulb that is meant to be used instead of an incandescent but it has a halogen setup inside. The PARs where pretty much mind blowing:

Driveway bulb: PAR120 at 3 feet.
The driveway parabolic is 100W.


Halogen "incandescent": PAR100 at 1 foot (and that is without any reflectors, just a bare bulb shining in all directions. With a reflector the PAR will be spectacular for sure).
The halogen "incandescent" is 72 watts. /u


Everybody will say that both bulbs run too hot. But try to get the same PAR from the same distance using LEDs - you will have to have serious cooling. T5HO on the other hand are tubes - they will run cooler but you cannot focus the light over a smaller tank for example. And don't forget that with the parabolic driveway bulb you can make shimmer. Same for the "incandescent" if you use a tight round reflector.

Both bulbs can be found in any hardware store. Very cheap ($3 and $10) and can be screwed in any incandescent bulb socket. I do think that both of them bend the rule "You can't have cheap AND great". The bulbs are the the rock bottom cheapest light setup one can get. And the performance kills both LEDs and T5HOs because there are no special ballast, drivers, etc.

The color of the light from both bulbs is about 5500K - not reddish at all but not stark white.

Michael

Is the driveway bulb a halogen also? I see a trip the hardware store in my near future!