$500 is crazy money for a used tank when you can buy a new one for about that price. I wouldn't pay more than $200 for it unless its something special but without knowing more about it I can't say.
All matter is merely energy condensed to a slow vibration, we are all one consciousness experiencing itself subjectively, there is no such thing as death life is only a dream which is an imagination of ourselves. Bill Hicks
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ua hua's 90 gal. high tech ua hua's 5,000 gal. water garden
It's pretty standard that the $1/g usually applies to aquariums up to 75g or so. After that the price per gallon goes up. 200 would be a good offer to start with plus whatever you think the stand is worth. $500 is entirely too much.
$500 I think is pricey for a used tank of that size, even with a stand. And I agree that $1 is a good rule of thumb but isn't always feasible when buying a tank over 100 gallons.
For example, last month I purchased a 160 gallon tank with stand off craigslist for the asking price of $350. Although to some, that may sound pricey, there were other factors to consider on why this tank was a good deal. Although the stand wasn't anything special, the tank itself was an older Oceanic with thick glass, had no leaks and was 7 feet long (dimensions you really can't find much). I was going to wheel and deal to get it all for $300 but it was a guy going off to college and needed the money. . . so I didn't try and negotiate. He was just looking to unload it and not make a profit. And the guy threw in some "fish stuff" that I plan to resell to make back a little of the money. SO, in the end it was a win-win!
But here's the thing. . .. I had been looking for some time. Unless your needing a big tank now, waiting for the best deals can be very rewarding HTH
He didn't bite on the $200 but it actually worked out. We were planning on redoing our floors..which was going to require a tear down of my 90 so it was the perfect time to upgrade...but we decided to remodel the guest bathroom first. Now I have plenty of time to look around.