Cool/cold water is difficult to do. Though things may have changed, I tried to do a cold water atlantic tank in 1990 or so and it was not easy. You need a high powered chiller, and I dont know what all else to keep critters who like it under 65 degrees or so, I didnt have the money at the time. Chillers cost mucho dinero and the operating expenses are huge too. I made a home made chiller from and old dorm room sized fridge and it did a lousy job, wont try that again.
Its one of those things in the back of my mind all the time though. If I ever find a good deal on a lobster tank ( like in restaurants and seafood shops), I might have to try it again. Frilled anemones are georgeous, and theres othe interesting critters from cold water. Also, its very unique, only place i've ever seen the stuff is at the National Aquarium.