One of the most important things to know about your bulbs in your hydroponic/indoor gardening setup.
Fluorescent light bulbs are the common ones seen in a modern nursery. Their low heat production makes them ideal for nurturing baby plants as well as leaf lettuce, spinach, and herbs. Fluorescents come in a variety of styles though most common is the T12.
Pros
- Inexpensive to purchase
- Inexpensive to operate
- Long service life—roughly 10-20 times that of an incandescent bulb
- Low heat production
Cons
- Florescents produce a narrow spectrum of cool light that is unsuitable for triggering the flowering response in plants.
Metal Halide (MH)
Metal halide, or MH, produces cool light in the range of 2700 to 5500 Kelvin and these very closely mimic natural light (which is partly why MH bulbs are becoming increasingly popular in public venues). For this reason it is an obvious choice for promoting vegetative growth. Horticultural versions are even available that also shine in the red spectrum as well.
Pros
- Very close to the spectrum of natural sunlight (6000K)
- Effective for promoting vegetative growth
- Long life span—lasting five times longer than incandescents (15,000 hours)
Cons
- Each uses a lot of power 250-1000 watts for average ballasts
- They operate under extremely high pressures (up to 20 atmospheres) and require special ballasts
- MH bulbs require a few minutes to warm up when initially switched on
- MH rigs: bulb, ballast, etc are not cheap, running into the thousands
High Pressure Sodium (HPS)
If you want something to flower or bear fruit, stick it under a High Pressure Sodium lamp. HPS rigs produce light in the warm, red end of the spectrum which is a nearly universal reproductive trigger in the plant world.
If the plants are only grown in red light, they grow all scraggly and nitrogen-starved.
Pros
- Superior flower production compared to MH or Florescent
- High energy efficiency – six times more light per watt output than an incandescent.
Cons
- Grows taller, wispier plants
- Plants appear washed out and nitrogen-starved due to the bulb’s poor color rendering (how accurately it depicts various colors of light)
Light Emitting Diodes (LED)
LEDs are new on the scene but could well be the future of indoor grow operations. They work like any other LED light, a bunch of low-wattage LEDs are arrayed on a circuit board and produce light. LEDs are, unlike other High Intensity Discharge (HID) rigs, exceedingly energy efficient. This is because they’re capable of producing the exact wavelength of light desired and no other. This means that an LED light programmed to shine at 5700K will shine at that an no other. Some LED rigs are also able to produce light at two distinct spectrum point simultaneously without any bleeding into other inefficient wavelengths and minimal heat production.
Pros
- Can produce dual band color spectrum (red and blue) at the same time
- Highly energy-efficient—nearly all wattage is converted into usable light
- Minimal heat production reduces A/C and heat sink costs
Cons
- Expensive to purchase—LED rigs can cost as much as large HID assemblies yet deliver light to less square-footage
