:Welcome: to AA! We hope ya enjoy
How long did it take for it to come back after replacing the water. I bet its because its still water and not enough surface movement (to me it looks like there is none). You can add air bubbles for pretty cheap or get a hob
filter that will make a little bit of a splash.
What filter do you have on it? Can you lower the water to make a splash or aim the output tubes up to create movement at the surface.