Has anyone had any trouble with water chemical levels after adding an aquatic frog to the tank? It almost seems like the frog is causing an imbalance. He is such a tiny frog but ever since we got him, the water has been off balance. He doesn't bother the fish, and the fish don't bother him, but something doesn't seem right. He is so cute, I would hate to get rid of him. Was he a bad bad choice?