I'm sorry, After rereading my post, I came off sounding very rude. Not my intention in any way!
I have a tank that I bought as a 47 gallon. After adding 40lbs of sand and 60lbs of rock I figured it would hold about 35 gallons. bought 40 to be sure and was short a couple gallons of water filling it. Dimensions were listed as 20x18x30. Turns out its actually 20x20x31 so about 8 gallons more. 60x18x21 would be 98 gal but manufactures routinely round up. Doesn't really matter, I hope I can maintain any one of my tanks for half the 40 years yours has been going!
I have a tank that I bought as a 47 gallon. After adding 40lbs of sand and 60lbs of rock I figured it would hold about 35 gallons. bought 40 to be sure and was short a couple gallons of water filling it. Dimensions were listed as 20x18x30. Turns out its actually 20x20x31 so about 8 gallons more. 60x18x21 would be 98 gal but manufactures routinely round up. Doesn't really matter, I hope I can maintain any one of my tanks for half the 40 years yours has been going!



