[Whatigot]

read the very first thing in the patent.
Number 1.
It refers to the way the fixture relates to the open top of the aquarium.
maybe you missed it, it's a little convoluted.
it's a little clearer if you click on the pdf image int he top left of that link you posted greenspot, go tp page 8, starting about line 27.

I have read that some of the issues with the patent are due to the similarities of the soalris design with this aspect of the patent.