I need some input on which tank to choose, 120 gal (48x24) or a 125
( 72x18 ). Which works better for aquascaping. I have never had overflows before. Do you put rock against them or do you build free standing?
I like my 120 quite a bit. I would not trade it for a 125 for anything. I think the extra width gives you a lot more options for aquascaping (so you don't have to have a wall of rock). It is also cheaper and easier to light since it is only 4feet long. The only tank I would want other than a 120 would be a cube about 48x48x20 or something.
p.s. you can look at my tank by clicking on the red house at the top of this post.
I agree that the 24" width of the 120 makes things a lot easier to aquascape as opposed to the 18" width of the 125. You can be a lot more creative. I wish I had the 24" width instead of the 18" that I have on my 75. Keep in mind also that, if you go with the longer 72" tank, and intend on lighting it with halides you will need 3 of them instead of 2 with a 48" tank.
What type of fish do you plan on keeping? Active fish like tangs would really enjoy the 72" length to wander your reefscape. This may be something to consider when deciding.
I chose the 125 because it's more conducive to tangs -- and I'll never own a tank shorter than 6' again. 120s are easier to aquascape, but you can fit something decent in a 125 if you work at it. Here's how I dealt with the overflows...