Just did a 50% wc on my betta's 10 gal, as I do weekly. I replace 50% of the water at The correct temp, add API stress coat +, and Prime. Always have had luck with that combo. Immediately after the wc tonight, my betta started opening and closing his mouth occasionally... more than just once every now and then. I fed him and he seems and looks and acts healthy otherwise. Any idea what he's doing? Is it a sign he is not getting enough O2? He swims to the top to get air as usual, and he ate happily tonight, as usual. Any clues?