This is an apparatus I have been using since 2011. I use a hydroponic tank which has no pump, no reservoir, and does not drain into anything. I used my hydroponic tank on my porch since it had plenty of light, though I now use it indoors and use two grow lamps and a heating mat (when the temperature drops below 50 something degrees F).
There should be a problem with stagnant cool water in my tank, but if I use this apparatus regularly, either every day or every 2 or 3 days, there is no rot or algae bloom. The sample holder, the copper sample tray, I fill will plant food which I have adjusted to my own ratio of minerals. I place it on the aluminum platform and apply 6V to it for usually around 1/2 hour a day. I use rechargeable batteries which I regularly recharge. I keep it at 6V or less which is very important to protect the seeds and subsequent plants from being fried by higher voltage.This is important as I found the higher voltages mask the advantage of using such a low voltage. The light from the apparatus when operating does not pass through plastic, glass, or paper. It does not pass very far by diffusion in the water media, but it will spread its effects evenly in all directions as a single swimming pool light spreads it light through a fair size swimming pool at night.
I have made various modifications on it since the summer of 2011. This model is by far the simplest and easiest to use, and easy to maintain and clean. I use it through the winter and get good results, however, I don't have it in a heated room. In the summer it does as well as I could ask for, considering I am still learning how to garden. The apparatus doesn't come with poles since I couldn't decide what length is suitable for general use. I recommend any dowel rod made of plastic, metal, wood, or glass. I use tomato stakes as they are good in water and easy to cut to use. As can be seen in the photos, the stakes are used to pin the apparatus in the hydroponic tank. My media has been vermiculite or perlite.