I'm trying out my old Metal Halide / High Pressure Sodium system for growing carnivorous plants. Most of my plants seem to be doing well so far, but the main issue I have noticed is heat buildup.
I have an electronic 250 watt dual MH/HPS ballast with your standard Home Depot-bought Sylvania Metal Halide bulb, installed with the cheapo reflector I got for free with the setup. I brought the plants in from the fairly cool nights we have had since fall started, so I think some of them are still in shock, like, "WTF happened we were just getting ready for winter and now it's 85 degrees!!" Here are a couple of pictures showing the setup as I have been running it for about a week. Half my plants are inside the 2.5gallon aquarium in back, the VFT's and other things that can handle drier conditions are in front.
Sorry if the other plants are in the way, I'm trying to see if sweet peas will root in plain water. There is a tiny D. rotundifolia and another King Henry you can't see in the aquarium
The problem is that by their nature, the bulb and reflector start to get very hot as soon as the light turns on. By the time I get home each day some of the plants outside the aquarium have nearly dried out already. To solve dryign out the first thing I guess I should do is get a big tray for everything outside the tank, but that still leaves the issue of excessive heat, both from the light itself being absorbed and re-emitted and also radiative heat from the bulb.
I know I can solve the problem by going out and spending $100 on a new cooled reflector, but I don't really want to invest in something that expensive for just a side hobby. I would ideally like to convert this reflector into something better without much cash investment. I have tried taping a piece of plexi to the reflector and it works for a bit, but the hot sides of the reflector are very hot and the adhesive quickly melts once the light is on for a couple hours.
First thing I need to try is moving the thing away from the wall, that should let a little more heat escape to that side.
The main tip I like so far is trying to find an aluminum mailbox and cut a hole in the side for a fixture, but those are nearly as expensive as a reflector! I will keep an eye out at the thrift store, but I decided to come here and see if anyone has any experience with HID's and carnivorous plants, or even if you have ideas for keeping the heat up and away from the plants.