Here's the complete circuit: https://dl.dropbox.com/u/19038241/Circuit.jpg
assembled: https://dl.dropbox.com/u/19038241/Assembled.JPG
You send a voltage proportional to the diode current back to the tracking pin - and there, constant current mode. I've seen this drive a pt-121 phlatlight at 30A no problem. You can add extra diode protection if you like, probably not ultimately necessary if you have a cap soldered to the diode already. Driving pump diodes: Done.
I think you're right Steve-o. 1W is good to start with. The maybe a polarized 2W from there??
PS - I like your video. Wear eye protection next time you goof.
Planters - I could research some thermal control circuits if that's needed? I've done some PID stuff in the past - maybe something with such a faster response is better to start with for best results?