I don't believe you could keep the water quality in a 10 stable enough for an anemone. The water quality in a 10 can go from perfect to dangerous in a matter of a few hours. They just don't have the water volume to correct itself. And some anemones get very large. I have a LTA that is a good 10 inches across. And a bubble that is a good 6 inches. In a 10 gallon, when the anemone expells its waste, it will be enough to totally pollute the tank and make it toxic for everything in there. That is why a 55 is the bare minimum suggested for anemones.