Is it common for an ADF to sit outside of the water for long periods of time or is this a sign that there is something wrong with the set up?

Why I ask, I have an ADF in a 5 gallon tank and have noticed that he will sit above the filter I have in the tank with most of his body out of the water and he will remain in this positon for at least 20 minutes.

Just a Question. He still eats and does not seem stressed just odd behavior.