I have been a marine aquarist for three years, and it has been quite a thrilling, and sometimes frustrating, hobby of mine. Now I have a tank that looks somewhat like a reef, perhaps a Pacific patch reef or rubble zone. I will try to talk about it in a later post. This tank has educated me about coral propagation and fish breeding (tank-raised animals I believe will enable us to maintain captive populations of reef organisms that will go extinct in the next few decades) the impossibly delicate water balance required to keep such corals and fish in health. Reef tanks have allowed thousands of amateur marine biologists like myself to make extensive observations on the habits of many organisms (albeit in a controlled environment, by no means perfect), helping scientists understand habits, food preferences, breeding behaviors, etc.
But what about the Deep Ocean? Aside from Tropical Reefs, I would posit in my unprofessional opinion that the Deep Oceans contain the second most threatened ecosystems, particularly Lophelia reefs and hydrothermal vents. Gulf of Mexico Lophelia reefs were hit particularly hard by the Deepwater Horizon spill and are extremely selectable to deep water trawling. Hydrothermal Vents contain unsurpassed species diversity in a mineral rich ecosystem. While somehow (another unanswered question!) species are able to survive the mercurial geological nature of these vents that are the lifeblood to these organisms, deep sea drilling will become a major industry in the next few decades (see Nautilus Minerals) We know nothing about how this ecosystem will cope with increased human activity, so we need to start picking up the pace on species description.
I'd like to see pressurized tanks that allow scientists, aquariums, and even hobbyists like myself to cheaply set up pressurized, cooled, dark tanks in which deep sea critters, be they pelagic jellies or benthic corals, can be observed over long periods of time. Sure we have subs and rovs that allow us to occasionally peak down into this environment, and we do have fixed data collecting stations (actually pretty cool - video) but none of these allow a consistent environment where experiments and observations are much easier, human contact becoming a constant.
Some pressurized tanks exist, such as this one for deep sea rockfish from Monterrey Bay Aquarium. See this discussion for a really good rundown of what technology is available for such a venture. I see several obstacles right now that are preventing us from enjoying aquariums of anglerfish and gulper eels in our living rooms; the pressure/temperature change from the time the organism leaves the depths until it reaches a pressurized tank is too much for many organisms, particularly fish whose swim bladders swell and gelatinous pelagic invertebrates which just disintegrate make just collecting organisms difficult (although some have tried - see this ngm article) Also, I'm no expert in physics, but to create cost-effective tanks with spacious viewing windows to contain water at a pressure of from 90-1000 atm seems near impossible.
Coral reefs are at the forefront of our imagination when we say Ocean Conservation because it is a highly accessibly environment; one can go to the aquarium downtown or build one in your own home for less than $2000. Although the glamor factor of deep sea worms is significantly less than sprawling brain corals, the uniqueness factor and importance of deep sea ecosystems should stand along with the recognition granted to reefs, polar seas, and mangroves. I believe the best way to do this will be to create these pressurized aquariums, so that we all can marvel at the deep.