"Paul" wrote in message ...
The problem isn't always with light escaping the hood when it's far above
the tank. A lot of light is lost because of the angle that it hits the
water, it simply reflects off the surface and get's bounced around in the
hood until it either escapes or gets absorbed. When you raise the height
of
light source the ang ecome less favourable for entering the water. So
even if you've got a perfectl losed hood, it's still best to have the
bulbs as close to the water as possible, unless of course your hood is
covered with mirrors inside.

Harry



Thanks for the help folks, appreciate it.


I had no idea how much light temperature could affect water
temperature. I have a 60gal tank which is almost 3ft deep and my 3x25w
tubes are doing a great job of keeping the temp around 24c and that's
with a temp sensor near the bottom of the tank. I'm restricted by the
tank length so couldn't go for higher watt tubes but I'll stick with
my restricted choice of low light plants and the trade off is I don't
need the heater (which I bought brand new....doh).