Hi Jacques, Both a 20 gallon tank and a 20 gallon long tank hold 20 gallons of water which equals to 75.8 liters. The difference between the two is the length of the tank as the name implies. 20 gallon long tank is longer but shorter in height. You can see the list of US standard size tanks at www.all-glass.com/products/aquariuims/index.asp Tomoko ------------------------------------------------------------------------- This is the apistogramma mailing list, apisto@listbox.com. For instructions on how to subscribe or unsubscribe or get help, email apisto-request@listbox.com. Search http://www.digital.com for "Apistogramma Mailing List Archives"!