I'm not sure what you mean by 'directly above the aquarium' ?  U mean hanging on top of the water surface?  UV is harmful to eyes, just any eyes, by damaging the retina.. You should not buy this type of bare UV tube.  This type of UV tube is for you to put into a covered area like a sumptank or somewhere that is not visible to anyone, any fish.  If you want to put it into the aquarium, the option is a concealed type like this : https://shopee.com.my/Hmeis-DeeTee-Aquarium...3962.5410713350

Hope this helps