I'm full of crazy ideas: This time, it's a lake functioning as an immersion exhibit with native Danish fishes and other freshwater wildlife. The lake would function just like any other lake; no filtration, no lighting, no nothing - except for control of the species mix and population. In short, mostly just an artificial lake. My setting of course demands natural pool or small lake proportions to work. Through this lake would be an underwater glass tunnel where people could view the scenery. Signs would explain the characteristics and biology of the various fish species found in the lake. As the lake would function relatively naturally, it would only require a minimum of maintenance; the viewing tunnel would just need to be kept appropiately algae-free, and most environmental issues (algae blooms and the like) could be managed through controlling the population and species mix of the fish. I think it would be a quite effective immersion exhibit, yet very cheap to maintain for such a large exhibit. Of course it wouldn't contain the very large or highly voracious predatory fishes, as it would still be a relatively small, and thereby quite fragile, freshwater habitat (again, pool or small lake; I think perhaps 0,5 hectare in size), but it would be capable of showing the often overlooked native fishes in their natural habitat. And at least when I imagine walking through the underwater tunnel - the fish swimming peacefully in their natural environment, the stalks of the water-lilies flowing with grace in the water, the sunlight creating patterns on the lake bottom from above - it looks absolutely stunning. But perhaps it only looks so in my imagination, and wouldn't be like that at all in real life. What do you folks think of my idea? Is this possible, and would it even look good? I'm looking forward to hear your responses!