imsqueak - I agree that their site doesn't have much detailed info. There are two connections for flexible hose on the bottom -you can see the red one (input) and a tiny bit of the blue one (output) in the picture. I believe those are connected to a metal pipe that winds it's way through the base of the chiller (kind of like a coil in a normal refrigerant chiller, only it is not coiled, it just kind of snakes around). I'm not an electrical genius by any means, but I think that a peltier device uses some kind of electronic transistor or some other kind of chip. When electricity is applied to the chip, it can transfer heat one direction or the other. So the chip is up against the metal pipe on one side and the heatsink on the other. I think there are two chips per heatsink/fan, so my unit with four fans has eight chips total. The water doesn't directly touch the heatsink or the chip. The fan just keep air flowing across the heatsink. The fans suck air in through the sides of the heatsinks that you see in the picture and then out through the top of the fan. The air coming off the heatsinks is cold when the unit is heating the water, and warm when the unit is cooling the water. And the rotation speed of the fans also varies a bit depending on how much cooling or heating is needed. I chose this kind of chiller for two reasons, number one it's not very loud (and I don't have a fish room or some other place to stick it, so I wanted it to be quieter) and number two, I like the fact that it draws just a little bit of electricity when all that's needed is a little bit of heating or cooling, so there's no giant spike in the current draw like a refrigerant chiller. Since the tank is only 58 gallons, the chiller should have a very low draw most of the time.
saycheesee - Let's just say I have too much invested in it! But I had a 72 gallon tank quite a few years ago, and when I had that one, I found myself buying some pieces of equipment several times (like skimmers and lighting and such). I'd buy something more towards the inexpensive end of the scale and then upgrade it. I discovered two things: (1) I don't like constantly fiddling with equipment just to get it to work and (2) the easier something is to perform maintenance on, the more likely I am to do the proper maintenance as often as I should. And so with this tank I spent a little more up front to get equipment that I won't be tempted to replace and to get stuff that was as easy as possible to perform maintenance on. Hopefully I'll come out okay in the long run.
Oh, and the tank is 58 gallons (Oceanic, 36" long, 18" wide, 21" deep) and the stand is for a 125/135 (72" long, 18" wide). The tank sits centered on the stand. I got the larger stand so I would have more room underneath for equipment. Especially being only 18" wide, there is not a lot of room at all underneath a normal stand for a 58 gallon, especially if you want to use external pumps.
