aropal

It remains a fact that three years ago Optolum as described in the link were managing to generate an everage of 83.3 lumens for 3 watts. Perhaps Optolum were not using the device your were referring to?

It does indeed appear to be rather an impressive claim and that is the reason I have specifically asked the manufacturer to confirm the 1w for 17w claim specifically.

Quite so, as originally suggested, even accepting the manufacturers claim of 17w equivalent for each fitting you would need at least four to produce the same amount of illumination as the two 35 watt Solux fittings.

Taking into account the refraction towards the normal created by the light moving from air to water the 35 degree led beam would produce a spot over 20cm in diameter for a light suspended 2 feet above the base of the aquarium.

Four such fittings would therefore continuously cover about a 20cm wide stripe along 80cm of tank floor; over two thirds of the length of a four foot aquarium. Of course the areas outside these pools of light would not be in total darkness due to the scattering effects of the light.

It would, I believe produce a pleasant effect if it were enough to penetrate 2 feet of water. Perhaps you have some data as to the absorbtion rate of water for light in the visible spectrum? I expect it would be significantly effected by tannins and suspended matter making definitive statements rather difficult.