UV sterilization before swimming pond inlet

Hi there,

I am looking for a recommendation to put some form of UV sterilization in line before the water inlet into my swimming pond. The water coming in is already pretty clean as it has undergone extensive wetland filtration. But there will be kids swimming in this pond/pool, so I would like to put in an additional sterilization step. Problem is, the water coming into the pond is gravity fed. I can't seem to find any gravity operated UV systems. Ideas?
The swimming pond does not have other filtration systems, as it relies on plant filtration and has a decent amount of water exchange through inlet & outlet. I guess I could put in a pressurized pond water filter system, and have the inlet run into that system (as well as feeding the system from the return from the pond)? But I rather avoid pumps in general.

Thanks!

If your wetland filter is extensive and working the UV-Sterilzation of the inlet water should not bring any benefit.

What happens to the water in the pond? Does it overflow somewhere or does it sit there?
Consider running a pump from the pond back to the wetland filter, i think the electricity is better invested here than in UV-sterilization of filtered water.