My first use of the PAR meter which Tom was so generous to loan me was to try to learn more about my simple 10 gallon tank. That tank has a DIY modification to its Perfecto hood, shown here: http://www.aquaticplantcentral.com/f...gal-light.html

One thing I wanted to find out is whether a simple reflector like I used there is effective. The answer is YES!! Very effective. Here is a graph of PAR readings for that fixture, with and without the reflectors. (The "without" curve is only two data points, with the rest calculated.)


You can easily see that those simple little reflectors come close to doubling the amount of light the fixture puts into the tank. This should help encourage people to make simple cheap modifications like this, when money is a problem.

The way I measured this data was to set the fixture up on a jig so I could do the measuring out in the open. To verify that this gives usable data I also got a single reading in the tank, in the water, to make sure the "air" data is close to the "water" data. Here is the setup for the "air" data:


I took readings at 11 places under the light, and at 8 distances below the light. I'm still working on the data to chart the variation in PAR throughout the tank, and I may post that later.