led panels

  1. GMCMaxx Member Member

  2. Sonfish Member Member

    Dunno, but if ya get them for sure post what you find out,
     

  3. David C Well Known Member Member

    See if there is any way to find out the lumens the LED's put out. This would help you compare them to standard lights on an equal level, Apples to apples. Otherwise I have no idea about the set-up, never seen it.

    Dave
     

  4. alexkent Initiate Member


  5. ruthven78 Member Member

    One such panel for sale at Big Al's says this (double led for $163):

    "This model is suitable for aquariums 36-48" in length. Includes 16 x 1W white and 8 x 60mW blue LED's (1200 Lumens)."
     
  6. Rearden Initiate Member

    Lumens are only relative when comparing light output of similar spectrum sources. They have more to do with how the human eye perceives light and not necessarily the power or strength of the output as it effects flora and fauna. Put more simply, lumens measure how we see light. The human eye sees a lot of green spectrum light, so lumens are heavily influenced by how strong the measured light source is in the green spectrum. Guess what spectrum plants don't need? Yup, green.

    Since LUX is a sort of density measurement of lumens it is also fairly useless for our purposes, as is the old watts per gallon rule which was basically intended to for the usage of older T-12 florescent bulbs which hardly anyone uses any more. Aside from that watts is just a measure of how much electricity is consumed by the device (amps X volts) and has little to do with evaluating lights beyond what they'll cost us to run.

    Another confusing reference is the comparison of degrees K or temperature of a bulb. Fluorescent tubes' output color is dependent upon the type of phosphors coating the inside of the glass. Electricity excites these phosphors and they emit differing wavelengths of energy. The "rating" is actually the average of the span. Put another way, if a tube's lowest temperature emission is 4,000 and its highest is 12,000 the bulb would typically be labeled 8,000. The problem with that is that a much more severely narrowed pattern of 7,000 to 9,000 would also receive the same rating. Obviously there is a much wider spectrum available from one than the other...and now because we're spreading the rated available energy over a wider number of wavelengths they will not be as intense in the mid range. Got a head ache yet?

    A more appropriate measure is the lamp's PAR (photosynthetic active radiation) rating, but the problem with that is that many manufacturers don't provide that information and most hobbyists don't own PAR/PPFD meters.

    Water acts as a prism, reflecting and refracting or bouncing and bending light waves. PAR readings are influenced by the depth of the intended tank, TDS present, surface turbulence, etc., and that's all before factoring in the reflectivity of the substrate and back ground. Shallow tanks with a white sand bottom will have very different requirements from deep tanks with black gravel and a black back ground. A 20g. long will require a different amount of light than a 20g. tall. More surface agitation will increase the amount of light that bounces off of the surface. Higher TDS will interfere with over all light transmission.

    Even within the PAR reading what we're looking for in aquaculture are principally two wave lengths of light energy, 430nm and 662nm. Plant species and their biology will determine which wave lengths they respond best to. Reds are absorbed by water more readily, and since what we see is a reflection of light bouncing off of objects we see deep water as blue because that is the prevalent reflected wavelength remaining after the water has absorbed or filtered out the reds.

    Most of the LEDs are high in the blue spectrum, which is good for plants, but deficient in the red spectrum, which plants also like. The blue-white LEDs should work but you'll need to mix in a few reds to fill your plants needs, but the red will also be in the visible spectrum so you'll have to play with it to get a balance and to keep your whole tank from appearing red. Different wavelengths are less effected traveling through water than others.

    Another pertinent variable when trying to evaluate lighting is the effect of the reflector. This is a whole separate area of discussion but suffice it to say that the gathering and directional focusing of the available light energy produced will have a significant impact on any lamps' practical effectiveness.

    Of course this all goes out the window as your plants grow, continually changing in their light requirements the closer to the light source they get and the more absorptive surfaces that they develop as new leaves appear. Then, right when everything is just perfect...you prune them back and we start all over again.

    And just how much does an aquatic PAR meter cost? Too much for most of us, but as a club level investment it seems within reach. Here's a link to one of the more affordable models:

    http://www.apogee-inst.com/quantummeter_options.htm
     
  7. Sonfish Member Member

    Very informative post Rearden thanks for sharing it with us,
    heres a link to a site Ive been doing some reading on, It has graphs and such that might help understand the diference in lighting, its a loooong read but it has picture lol
    I reckon it helps if I post the link, me thinks I need more coffee lol :eek:
    http:///Aquarium_Lighting.html
     
  8. Nate McFin Well Known Member Member

    Big time;D
    Seriously though great info thanks for taking the time to post it!
    -Nate