Please read the following article on UV sterilization.
http://www.americanaquariumproducts....ilization.html
I have a submersible unit (18W Resun UV-05) but the one I have does take some room inside my tank. Since it's a 6 footer, 145gal tank, I found the way to hide it behind
driftwood, planted pots, Indian Almond Leaves...
Not all UV units available for sale work well, you are doing great by asking around.
Thank you for sharing this, now I will look around this particular design.
Pepe
Santo Domingo