Freshwater HOB AS-- question about wattage.

[Orion5]

Hey everyone!

I'm really glad I found this forum! It has been incredibly helpful.

I do have a question though which might not be simply answered: Is there a wattage/square inch of light required that is a flat number regardless of tank size? My tentative plan is to use a 12" x 12" 45W LED grow light panel on a screen the same size for my scrubber. That makes a little over 3W/inch if I calculate correctly. I've read other threads where it has been indicated that 1/4 to 1/2 W per square inch is enough, and another that stated if a heat sink is not required then the intensity isn't high enough. Any thoughts?


Thanks for your patience and expertise, and have a great day!

[Floyd R Turbo]

First things first, have you read the Algae Scrubber Basics (http://algaescrubber.net/forums/showthread.php?1291-Algae-Scrubber-Basics-The-Summary)thread?

The screens are currently sized based loosely on feeding quantity, not tank size.

As for the LED fixture you mention, I'm pretty sure I know the one you are referring to and it may or may not work. These large arrays usually use low-power 0.1W LEDs and they are just not intense enough, nor are they likely the proper spectrum. As a general rule of thumb, if it doesn't need a heat sink, it's not powerful enough, IMO.

As for watt/in, when talking 3W LEDs at 700mA drive current, my recommendation has been one 3W LED on each side of each 2"x2" section (maximum density) or 4"x4" section (minimum density), at 2" distance with a diffuser or 3" or more away with no diffuser. That's kind of a loose-general guideline, but it seems to be working well.

For 1W LEDs, cram then as close as you can to one another and place about 2" from the screen with no diffuser. To my knowledge, not many have tried this, simply because 1W LEDs are going by the wayside, all improvements are being made to 3W LEDs. 1W has pretty much stayed the same for over a year, while 3W continues to develop higher and higher efficiency.

[Orion5]

Floyd-- Thank you so much for this valuable, detailed information! I'm relatively new to forums, and so I didn't locate that post you linked about AS basics. A wealth of information and ideas.

My experience with the 12" x 12" red/blue LED grow light panel is with terrestrial plants, and they do encourage a lot of growth when placed at a relatively close distance (12 inches or less, depending on the size of the plant and if it's a seedling or not.) I am assuming that since it the screen and the light panel will be less than 1" from each other that it will produce some algae growth, but maybe you can enlighten me on this-- because I am assuming that algae require pretty much the same lighting conditions as the terrestrial plants I've more experience with. I guess we'll see-- it's fun to experiment. Do you think that the same lighting applies, or will it work but be much less efficient or even useless as a scrubber?

[rleahaines]

Orion,

I tried the light panel you are talking about. Didn't work at all for a light source for a scrubber. The light is too weak and diffused. I thought it should work, but it didn't.

[Orion5]

Wow! Thanks so much. That saves me a LOT of time.

Was it stuck right on the plexiglass covering the screen? I'm just curious.