i came home this afternoon to find one of my roseline sharks, and albino rainbow shark floating in my tank. i also noticed my puffer had changed color, instead of green black and yellow, he was pretty much all brown. i changed 50% of my water and my puffer freaked out and started biting some of my plants in there, and then fell over stiff, i dug him out thinking he died but i saw he was still breathing. i rushed him to my 10 gallon tank and he puffed up, i thought he was going to explode. he then layed on his back and stayed like that for a good 3-4 mins. i thought i lost him again but saw him breathing. WHAT ON EARTH IS GOING ON!!!!!!!!!!!!!!!!! im going to petsmart now to get my water tested, any help will be greatly appriciated!!!!!!!!!!!