I've had my betta Castiel for a while now, and I've done full and partial water changes as often as needed. Nothing has ever happened before.
But last night I did a partial water change and this morning he is just laying at the bottom of the tank, only coming up for air. I didn't change anything that I've done before. (Aging the water, de-clorinating it, same temp. slowly adding etc) I'm really worried that there was something in the water and now he's just lifeless. At first he was swimming around like crazy when I first changed the water, now he's staying at the bottom.
The water temp is the same as always (78/79 degrees) and I've changed nothing but the water. Any ideas? It breaks my heart to see him like this, he's usually such a goofball.