Why was the biosphere 2 experiment considers a failure?

Bio sphere II was not self-sustaining if outside oxygen had to be added in order for the crew to survive. As it turned out, the problem had more to do with carbon dioxide than with oxygen. Biosphere II's soil, especially in the rain forest and savanna areas, is unusually rich in organic material.

The higher you go up the less oxygen there is 

That is false even though water expands when frozen nothing changes at all