in 1 part of my dream layout(Parents are party poopers)there will be a pond with a boy fishing has anyone ever put fish in fake water.
I’ve heard of using a bit of tin foil and some permanent fine felt tip markers to make some tiny fish for ponds and streams. You then pour the water in layers and embed them on top of one of the layers before you pour the next layer on top of them.
If you are talking about putting real water on the layout with some tiny minows in them, real water does not scale well and stagnant water is a great breeding ground for insects and all kinds of stuff that grows.
John Allen discovered when he tried to use real water that the humidity levels in his house shot up when he had real water in the train room. He quickly changed his plans based on that discovery and went with cast resin water elsewhere.