Does the acrylic scratch over time? I know it is a lot lighter, but is the material more sensitive to scratching. Also, Didn’t you make your 240g?I have a pair of 4x2x2 120s which are my poly tanks, Granted my biggest poly right now is not a huge one, but my ornate is close to 12" and there's multiple dels that are 10-11" with him and a few smaller ones and the 4x2x2 works fine for me. I like the 2ft front to back better than my 125g which is 18".
All my tanks have been used when I bought them. Tanks like 90g,120g,6ft 125g usually are going to be fine if the seals look good and they are not real old. The biggest problem with most leakers are either that the tank is old (20 yrs or more) or they are big tanks that have been moved a number of times. For instance a 15+yr old 180g or 220g doesn't take to being moved around a lot. That's how a lot of those older big tanks pop seals. I found that out the hard way about 5 yrs ago. I bought a 7ftx2x30" 265g glass tank that was up and running for years with a guy in my club no problem. It was drained and then we carried it down the stairs at my house and it leaked. After that I swore off glass tanks for anything over 125g. Thats why I went with acrylic on my 240g. If you can afford it then look into a used acrylic, that way there is no worry about it. There's deals to be found on good used acrylic tanks. I picked up my 6x2x30" 240g acrylic a couple years ago for $450.

We looked at 125s at Petsmart recently, I liked the extra width of the 120g 2X4X2 but not the height. He liked the 6 foot length of the 125g 6x18inx2ish. Needless to say, I'm considering a 125 or a 180 with a cool background like