To be perfectly honest I've never actually measured mine. I have two in a 40 gallon tank and like Unnar said I just made sure they have a shallow area to rest in the water..a deep area for real swimming and diving, and access to a land area. That's what I love about the 40 gallon is I was able to give them several different places. What I did for mine was make it mostly aquatic by filling the entire bottom up with water. In order to get a good visual for you I just now measured the depth of my water and it's 4 inches deep. I have a dull edged piece of glass (originally used for a glass shelf that I threw out) and I have that propped up in the tank with jungle mix over the top of it for their land. There is a turned over water dish and hollow log underneath the glass to hold it up and secure it. I have moss in and out of the water, the moss helps to give them the shallow areas as does the turned over water dish. It also helps them climb onto the dry land. The filter is tipped to run water onto the moss and back down into the main water supply, and it is covered with fake plants to sort of hide it.

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At the time this photo was taken I had a quarantine tank holding one baby frog so I apologize for the eye sore. But I hope this helps.