I purchased the Periha Drop-in Submersible UV-C Sterilizers × 1 40W - Periha Submersible UV Clarifier for my pond. I placed it near the filter area that is close to waterfall and covered the filter box so the light wouldn't affect birds, fish, toads, etc. After just a few hours found a dead toad. Moved it to skimmer box and again covered box. Within a few hours one dead fish and several more dead toads. Requested a refund as this unit was literally in my pond less than 1 day and was told by management they have a no refund policy on a "used" product. I also ordered hyacinths and water lettuce. Neither are looking well and I will have to replace. This is my first and last purchase with this company.