Ka-ching!!!!! If I could go wild it would quite possibly include a water feature. Water is a powerful set design tool. It has its limitations, and it's a challenge with huge rewards.
The most common trouble with water features, eg aquariums and fountains, is the noise that they produce. Sometimes a fountain can be worked with without too much trouble, if it is an out door shoot. Inside, like with aquariums, the noise of the pumps are a real problem. It can be worked out, but it needs addressing ahead of time, not when the Unit decides it's a problem; you'll lose your water feature.
I love aquariums because they double as a layer.
Ponds are my favoirite. I love ponds because you get to play with the lighting on the water and the reflections are sensual. No lighting program can reproduce the natural beauty, or generate a mood like reflected water lighting.
Either the set is on a platform, the pond below, or the pond is a pool enclosed by a 'stone' wall. Depending on the size of the pool, you probably need an engineer to verify your floor can take the weight. If you want a Grip stirring the pool, it needs to be designed with an off-cam access, eg. against a wall.
Sometimes the set is half full of water, and nasty products like Marine Enamel need to be used. When someone tells me they need to use Marine Enamel for a set I remind; Marine Enamel is an extremely toxic product, and, ultimately some poor desperate painter will be nominated to use the product, and too often they are unaware of the hazards. Too often the shop crew take a design as a final, no negotiations. They will use the Enamel, even without the proper gear. They are dedicated.
As a Production Designer it is your responsibility to ensure that no one gets hurt as a result of your design. Sometimes there are other ways to do it. Coming up with solutions is what Production Design is all about.
Water = Expensive stuff!