You have a beautiful pond! Maybe you can assist me.
I purchased a home recently, and a water-garden pond with gold fish came with the deal.
When running the water pump, the water evaporates very quickly.
I had someone come out, look at the pond and advise me. He removed my water plant from the pond and pulled it apart (stating the plant needed to be pruned). He told me to disconnect the hose from the pump to keep motion in the water. Also, there is a leak somewhere; water runs around the side of the pond when running the pump. I have a UV, but was told not to use it, mainly because of not knowing how old the bulb is, or if it needs to be replaced. The seller left a net to cover the pond from debris and animals. The seller told me that algae protection is also in the pond.
I'm very concerned for my fish, their behavior has changed. They are swimming close to one another and very close to the edge of the pond. My pond looks similiar to yours, pertaining to size and depth.
Please advise. I have read several articles on the internet, and have little knowledge concerning water ponds.