Huge environmental downside with reef tanks...
...unless you're fanatically conscientious. Granted coral and saltwater species propagation is better now than in years past but much of the stuff at the LFS is just ripped out of a reef somewhere in the world. Hell, using dynamite and chemicals to stun fish in coastal areas is still widely employed all over the world, and whatever mortality rates are for freshwater species in shipment I'd reckon are way higher for oceanics.
Now if you can buy coral from someone who grew it and fish from someone who spawned them or can give some credible assurance that collection was done with some modicum of ecological respect/sensitivity, go for it, but otherwise the coral in your tank is a hole in a reef somewhere (that's likely already acutely suffering from increased siltation, pollutants, temperature, and UV, etc.) and who knows how many fish died to get you the one or two that you can/will probably never breed. They're are whole areas in the Philippines for instance that were just stripped for the saltwater trade. Just ask the guys at House of Tropicals in Glenn Burnie store where they get their coral and watch them stutter about how they really have "no idea".
Too high a price for me to enjoy no matter the visual splendor. Fact is most saltwater tanks are just black holes for reef species. And that's part of the beauty of cichlids and catfish - you can have stunning displays without any wild specimens (or ecological liability), and breed them yourself to perpetuate a cycle that doesn't come at the expense of nature.
