High Pressure Sodium??

[dred]

I just happen to have this 150W High Pressure Sodium light from some hydroponics experiments I played with back in college. At that time High Pressure Sodium was supposed to enhance flowering, whereas metal halide was said to maximize vegitative growth.

Is there any problem with using high pressure sodium on a very lightly planted tank (two small amazon swords)? Will the swords grow - tank is 24" tall.

Yes, I think the blue spectrum of a MH would be more visually appealing, but I want to make sure I'm not feeding some undesireables by using the more yellow spectrum of high pressure sodium.

Thanks, milton

[ronrca]

The appearance of HPS lighting is very yellow! Take a look at the street lights at night. Not very appealing! The Color Rendering Index (CRI) is poor, 32! Incandescents are 97. Fluorescents (cool white) - 87. You can get better CRI with HPS lamps though.

THe color temp is around 2100K therefore not really ideal. You want to be aiming for aroud 5000-5500K which is sunlight at noon.

A draw back of HPS lighting is the heat that is given off (well, at least you dont need heater)! ;)

[yellow sub]

I have always wondered about using HPS lamps for growing plants. As far as the spectrum goes, it sucks for our eyes. But they are supposted to be the most effecient way of generating light there is.

I have always thought, but never did, of creating a system where I would use HPS lamps during the day while I was out at work and wouldn't be bothered by the narrow specturm. I would also balance this out in the blue end with some 6700 K florescents. Then have them on timers and when I got home just use some full spectrum florescents for my viewing pleasure.

Stephen

[ronrca]

Yes! You are correct! HPS are very efficient lighting! It would be a good experiment for sure! One thing to remember is that plants are not too fussy about sprectrum (it helps slightly though). They prefer lots of light.

How efficient? Well, first we need to define efficiency! It is defined as lumens (the actual output of a light source) per watt (the actual power consumption of a light source).
So, the efficiency of a HPS is around at least 100%+ (not taking into account ballast losses). Fluorescents is around 80%.

The quesion remains though, how does the low sprectrum effect the plants and algae?

[dred]

Well,

I set it up on the tank for a week. The light was very, very yellow. I asked the question because the amazon swords didn't seem to be responding well (yellowing).

Then I tried a pair of 40W T12 "daylight spectrum" bulbs - much nicer look. The tank has had one T12 light cycle so far, and the green is noticeably deeper on the amazon swords.

If I ever run across a local grow shop, I'll try to source a MH bulb that is compatible with the HPS ballast, but it's back to storage with the HPS fixture for now. Even if I'm imagining the plant response, the whiter light is just that much more visually appealing.

Guess I was hoping that the HPS light spectrum would be good for flowering aquatic plants.

milton

[stygian7]

I think high intensity discharge lamps have a bad rep for generating too much heat. There are a couple reasons for this.
1. HID are a spot light source-and thus a spot heat source as well. Fluorescent lamps produce a significant amount of heat also, however, this heat is diffused over the entire tube, so it doesn't seem as hot.
2. HID tend to be higher wattage than most fluorescent light systems, thus they produce a greater total amount of heat.

HID lamps are the most efficient form of lighting (allthough I've heard that initially fluorex lamps have a few lumens higher efficiency), which means that they must actually produce less heat per watt than a fluorescent, right?

I'm not 100% positive about this, so please correct me if I'm wrong.

One more thing about point lighting sources is that they create really stunning reflections on the bottom of the tank and throughout the room.



The appearance of HPS lighting is very yellow! Take a look at the street lights at night. Not very appealing! The Color Rendering Index (CRI) is poor, 32! Incandescents are 97. Fluorescents (cool white) - 87. You can get better CRI with HPS lamps though.

THe color temp is around 2100K therefore not really ideal. You want to be aiming for aroud 5000-5500K which is sunlight at noon.

A draw back of HPS lighting is the heat that is given off (well, at least you dont need heater)! ;)