GEM5 ® lights, which are also used in the RAIN2 and RAIN4 models, can be put underwater like on the right side of this DIY waterfall screen that someone made using my 2008 design (see ats2008.org) Or, the lights can be above water, like on the left side of this screen. This is because the lights are underwater submersible, but are also made of a material that keeps the LEDs cool when operating out of the water, without needing to reduce the wattage/power/light at all. Any LED light strong enough to grow good algae will get very warm when not in the water, and it needs to be able to handle this heat.

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