You cold use the micro mesh polishing cloths. They are basically like sandpaper but on a cloth backing and go to 12,000 grit. They are meant for wet sanding so you could probably use it inside the tank. I doubt the small amount of plastic dust released into the water would harm anything and could probably be mostly removed by filtering and a couple of water changes. I believe they were originally made to polish scratches out of acrylic aircraft windows so they would be perfect for acrylic tanks.

You can buff out acrylic scratches on the inside without emptying the tank, lost of various kits available and you can attach the buffing pads to magnets to make the process easier.

JUST MY OPINION but don't try to polish or buff out acrylic when its filled with water. your hand movement will stir up sand or detritus which will get into the cloth and then scratch ur acrylic even more. Personally i hate acrylic because of the scratches and the benefit of having acrylic is only when you move the tank in place or removing the tank. my experience is acrylic scratches very easily but are usually so fine you can't see it but the fine scratches compound to be visible after sometime.

I would definitely beg to differ in my experience. Acrylic scratches far too easily when you've got a reef even if you are extremely careful because virtually anything - a speck of sand caught in a magfloat, moving a piece of liverock, even a frag that falls - can cause a scratch. While you can buff you scratches, it is a massive PITA after you've done it a few times and it always seems that right after you've buffed out one another one appears. Reefkeeping is high maintenance enough without having to add another job to the mix.

Yes acrylic scratches easily when compared to glass but lets not get carried away. My point was it won't scratch from sand blowing around the tank. A glass tank will also scratch if rocks or corals fall against it or if sand gets stuck in your magnet cleaner. I've owned my fair share of acrylic tanks and have worked with acrylic for years, you simply have to be a little more careful and only use cleaning products made for acrylic.

Its 14 inches deep, 16" long and 3/8" thick there might be 13.5" of water in it bust most likely 13" there isnt alot of pressure, that acrylic isnt going to bend.

I think what it will all boil down to is personal preference and how you are with your maintenance, I swore I would never have another acrylic tank yet here I am, VERY happy with mine, I do find it is easier to clean but I am cleaning more frequent, I am only doing a FOWLR and I am not so sure I would use acrylic for a reef as scraping coraline could prove more damaging. I have successfully buffed out a few minor scratches both on the inside and outside. Comparitively speaking I feel this tank at 5 years old looks as good as or better than any glass tank I have had set up for the same amount of time and will only be better as it ages (never have to deal with discolored or peeling silicone in the corners)

Got a message back from the seller, shipping is an extra $30. So all in all it comes to $190. From what I had investigated previously, it seems like a great deal. I wanted to get a small starphire rimless cube, and I believe the quote I got a while ago was much more (without shipping)

I think i'm going to go for it, I'll let you guys know how it turns out.

You're right what do I know about a few mm of deflection

http://i11.photobucket.com/albums/a1...nkCellCast.jpg

http://i11.photobucket.com/albums/a1...iniousCast.jpg

http://i11.photobucket.com/albums/a1.../glasstank.jpg

Cool graphs! How'd you do those up? If i'me reading it correctly the 16x16x14 should (in theory) only deflect 1mm?

Submited an offer to him, so I should have the tank in the next couple of weeks!

EDIT: He just accepted it, whoot. $90 instead of the listed $114, almost takes care of the extra shipping cost to canada