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so, i was shopping on lll reptile in the waterland tubs, and i noticed that the sizes were 18 gallons, 65 gallons, 200 gallons. i was looking for a 75 gallon for skipper.
so i remembered that an adult female was supposed to have a 75 gallon AQUIARIUM not 75 gallons of WATER! the wateland tub said can HOLD up to 65 gallons of water, and that didn't incude the land area! most people use an in-tank basking platform so that takes up half the water, so this is BETTER than a 75 gallon aquarium!

as for the other sizes,a hatchling needs a 20 gallon AQUARIUM not 20 gallons of water, so, 18 gallons, perfect size! and 200 gallons os perfect for breeding, just 2 turtles or just spoiling a turtle.

The aquarium vs water is debatable. I think a lot of people have been using ATBAs, so their majority of the tank contains water.

Yea Steve. I disagree with Skippah. A 75 gallon tank holds 75 gallons of water that's why that size of tank or larger is recommended. An in tank basking platform by itself only takes away some surface area it alone doesn't take away gallons of water. And as Steve said most people use ATBA's. And an in tank basking platform does not take up half the water in a tank. Filling the tank half full does!

A 75 gallon tank holds just slightly less than 75 gallons of water. The volume of the tank is calculated using the outside dimensions of the glass but the glass has some thickness so the inside volume is a bit less. In either case if you're a little off from the recommended size your turtle will be fine.