Led lighting strength

[Fishies86]

Hi,
I'm looking at upgrading my lighting. I need at least a 20w light.

I've been on eBay just to have a look around and see what's available.

I've seen a lot of LED lights, but they don't tell me what wattage they are, only how many lights there are.

Does anybody know what wattage an LED light is, so that I can work out what strength a strip of them would be.

Are LEDs recommended? I don't know much about them at all

 

[BigJim]

What do you want to do with your lighting? Are you keeping live plants, or just looking at your fish?

Small LEDs like you typically find on eBay don't show wattage because they don't use much power. They also don't put out enough light to sustain plants. If you want to calculate the power: Watts = Volts * Amps.

If you're looking to support live plants, you'll need some more powerful LEDS. I'm working on a fixture using Cree XR-E Q5 LEDs. They're rated at 3.7V at 1A for a power rating of 3.7W.

None of this information will tell you how much light the LED is emitting though, just the power dissipated through the LED. Some of it is converted to heat. At the very least you'll need a lumen rating and even that is sketchy. For aquariums, the best way to determine an LED's suitability is to set it up and measure it's PAR (photosynthetically available radiation) at the bottom of the tank. PAR meters are expensive though, so I'm basing my design off the designs of others who have had success.

If I get the chance and I'm feeling motivated, I'll post some pictures of my fixture when I'm done with it in the DIY forum.

 

[Fishies86]

Thank you
I want the lighting for my plants.
I've got a 10 (uk)gallon tank with a 15 watt daylight bulb that came with the tank. It also came with a blue moonlight bulb, but I don't have that switched on very much. It's a blue light, and as far as I remember from school plants don't absorb blue light.
From what I've read, I need at least 2w per gallon. (is that per American gallon? I didn't think about that before)
The bulb in the hood is like a home energy saving light bulb. I can't fit a strip light in there because there's not enough space, so I was looking for an alternative.

 

[Fishies86]

Maybe I could just replace the blue bulb with another daylight one. That would give me 30watts, which should be enough shouldn't it?

 

[jenatron]

Typically the watts per gallon you see are American gallons, unless stated otherwise. The watts per gallon you need is dictated by what you want to grow. When you decide what you want to grow, then we can tell you what lighting you need, and if you'll need a higher-tech setup along with it.

Edit: This was directed towards the statement about getting another CFL. I realized after BigJim's post that it was unclear.

 

[Fishies86]

At the moment I've got two amazon swords (echinodorus), elodea, purple stricta and umbrella fern (I don't have the Latin names for the last two, and I'm pretty sure they're not aquatic even though they're in my aquatic book!)
I'm going to keep the non aquatics until they start to rot, then I will replace them wit something else. I'm a bit limited with what plants I can get here though.
I quite like the look of vallisneria, and possibly some cabomba. I don't know anything about them really though, so I don't know what lighting they need.
I have heard that the amazon swords I've already got will need more light than I have presently.

 

[BigJim]

There's probably more information at this link than you want to know: Aquarium Lighting; Kelvin, Nanometers, PAR, Bulb, Watt, MH, LED, Light Basics.

The Wpg rule doesn't transfer well to LEDs. It's rough enough as it is for fluorescent lights. LEDs are directional so they put all their light down into the tank. You don't have to deal with restrike and reflectors.

I did a lot of research before I sprung for the LEDs I'm working with. I found a lighting experiment someone did on a reef tank comparing high-power LEDs to T5HO lights. This person had the luxury of access to a PAR meter, which is really the only way to quantify light strength for plants or coral. The LEDs were better than the T5HO at all depths.

If you're just aiming for the 2Wpg threshold, retrofitting another CFL or just using a bigger CFL would be your best option as far as cost goes.

LED technology has a high buy-in cost at the moment. I'm messing with it now because I think it's going to be the future of lighting and I'm a nerdy engineer. I'm building a fixture for my 20H and I figure I've got $70-$80 invested into my LED light so far. That figure doesn't include time or the tools I purchased and I'm not 100% confident my design will work as intended. I may have to spend some more money for heat sinks, but I'm hoping I don't have to.