UV Sterilizing

[wjuniorbr]

I have a tank with about 700 liters of water and about 400kg of epsom salt (sulfate magnesium), the tank is about 2.2m x 1,1m and only 25 cm of water in height. Im using a sand filter (like the swimming pool ones) to filter the water, I want to add a uv sterilizer to kill germs and bacterias that might still stay alive. First I thought about adding the sterilizer in the same pipeline of the pump that pumps the water to the sand filter, but then I ll be reducing the flow of water and thus forcing the pump. So I thought (and that is my doubt) to use a lid the tank with 3 or 4 15W uv tubular light bulbs under the lid close enough to the water, and turn it on while the water is being filtered by the sand filter so that the water will be circulating and all the water will get close enough to the light to kill the germs.
Will this work? The same? worse or better than the standard uv sterilizer?

Thanks for the help in advance