Low lighting for emersed growth?
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Old 07-21-2012, 03:04 PM   #1
nicks7.1985
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Low lighting for emersed growth?


Hi all ...the way i seem to understand it is..

if i have 2 identical setups one submersed one emersed both with say 20w light, the emersed will get a higher PAR as the light wont have to go through the water.

Does that mean that i can use the same light levels over an emersed setup as i would over a reg submersed setup and the plants should grow just a bit faster?


i realize i can blast pretty much all the light i can afford over emersed, but thats the problem lol...cant afford it haha. so im trying to figure out a minimum amount of light to use and still get regular (medium light) gowth for some hygro tiger that i have., then increase it from there..any suggestions?

thanks!,
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Old 07-21-2012, 06:46 PM   #2
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You get more PAR with water in the tank than without water. The air to water interface slightly focuses the light, because off center rays are refracted a bit towards the center. And, with water in the tank the glass to air interface at the front, back and ends of the tank reflects a lot of light back into the tank, increasing the PAR near the glass.

Many of the aquatic plants we grow are found in partial to full shade in nature, so they are not adapted to grow in full sunlight - 1500-2000 micromols of PAR. I haven't found a good reference for the PAR in open shade or full shade, but it is probably around 500 micromols. So, if you want to use the maximum light that might be used by emersed plants, you could try for something around 200 to 500 micromols. That would be extremely high light for an aquarium.

You can get a lot of light, without spending a lot, by using 23-25 watt CFL screw-in bulbs in dome shaped reflectors less than 15 inches from the plants. I think that is what I would try if I wanted fast emersed growth.
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Old 07-21-2012, 10:59 PM   #3
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hoppy u r the man dude...maybe i should have pm'ed you on this lol ...you pretty much ans all my lighting questions anyway haha. thanks a lot for the info as always, it is appreciated!

one thing ...so if i used the same light 54w that is over my tank, the plants should still grow emersed..just slower?
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Old 07-21-2012, 11:44 PM   #4
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I believe the plants will grow ok with the one bulb T5HO light. I doubt that many people try to overwhelm their dry start plants with a load of light. And, the dry start method has worked for a lot of people.
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Old 07-22-2012, 05:36 AM   #5
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i just set it up tonight and have 2x t5ho 54watt bulbs about 15 inches over the tubs. the lights are over a year old but still are quite bright...although i know it dosent mean they have the right wavelengths or w.e anymore,,,but we'll see what happens. ill put up some pics every week in the journal section.

i did set up 5 different tubs a bit differently and recorded them all with pics to see which works best..if it works at all.
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