I built a home around a 15,000 gallon tank that I had ATM build.Pictures were posted around march.I have a well that I used to fill the tank and there is to much iron in the water.The fish are doing great. 30' x 10' x 6.5' on a 2 foot stand.
2000 gallon mom and pop fish store, i guess that counts.
too of the local fish stores near me got into a pissing contest, it started with 400 gallon display and they kept moving up until they hit the thousands.
Except for those on the internet and in commercial establishments (resurants, aquariums and pet stores) the largest I have ever seen in a home is a 210. Its in my living room.
I used to live 5 minutes (walking) from the Monterey bay aquarium. So there open water tank takes the cake I don't recall how many million gallons it is. I cant wait to move back home