Cold water tanks

[dr_girlfriend]

Does anyone here keep cold water tanks? I was reading up on them (what limited infor there is) and it seems quite interesting. I'd like someday in the future to keep one and have a nice mix of macro algae and coralines.
Another question, I'm planning on getting sand from the ocean wich is sub-tropical for my tank. I'm going to be using it probably in a tropical tank, temp around 76-78. Do you think the bacteria and any life forms would be ok slowly transitioning to a warmer temp?

 

[malkore]

The bacteria should survive I'd think...however the other stuff, I'm not sure. I'm nowhere near an ocean (though I've seen both the Pacific and the Atlantic), and not a big proponent of buying live sand from the LFS, so I just dunno what kinds of life you could expect in beach sand, let alone if it'll survive.