On Sat, 26 Nov 2005 22:56:41 GMT, "Ann R" wrote:

Just an observation. Doesn't the depth of the tank, and the the wattage of
the fixture have something to do with what can and can't be grown in a tank?
Take a 50 watt bulb and put it over a 30" tall tank and the tank will be
dark. Put that same 50 watts over a 12" tall tank and you have a bright
tank.

Ann,

Yes the depth matters tremendously. After 2' (60 cms) deep, the light
penetration reduces dramatically. Scientifically, I think it works on
the inverse square principle, in that the light at double the distance
is only a quarter of the light intensity, not half as you may expect,
and so on. If you read expensive aquarium books, where optimum light
is accurately measured at different depths (the Modern Coral Reef
Aquarium etc.), light penetration drops off significantly after about
5 metres.

Regards, Fishnut.