Yes, it will work under your hood as long as there is a place for the power cord to come out. They either attach with two suction cups or the hanger being used in that picture. You will not be able to fill your tank up completely. Not being familiar with the Eclipse hood/tanks, I don't know just how far down your visible water line will be. If you're going with the Water Wonders decoration, I'd measure to be sure it will fit.
Edited:
From the PetSmart website the Water Wonders dimensions are
# 10-gallon unit measures approximately 9"L x 5"W x 12"H.
# 20-gallon unit measures approximately 10"L x 5"W x 16.5"H.
The Eclipse System 12 measures 21"L x 11"W x 18"H.
If you went with the 10 gallon size you'd have 4 to 6 inches of dead space above the filter (depending on your gravel depth). You'd be better off with the 20 gallon size.