Looked it up on the net and looks good. Although, whenever these products do not share info about the lamp and the light spectrum, in µWs/cm² or other measurements, then this raises my skepticsm, but, from the price of the product for a 13watt sterilizer, it makes sense, that is assuming by just looking at price can be any indicator.
You will notice there is a valve there on the fountain stem. Over time of being used and being turned on/off, the bulb will lose its strength and this is when you would start closing the valve on the stem.
These devices work on the concept of freely submerged UV devices, that is meaning the device does not connect to pipes and water flows over the bulb in a container. I have seen many DIY implementations of this approach of UV devices. I am not entirely convinced on their efficacy.
Although, I like the design of how this particular device by Aquatop, except not enough specification information about bulb and lamp is shared to know its performance. So, without knowing this information, not for sure if the full flow of 2,700gph is too much or too little. For the flow to be allowed that high and still be a sterilizer, then the lamp and UV bulb would have to be quite strong and I would have expected a much higher price tag.