Hello! I have just gotten my 20-gallon hexagon aquarium going 3 days ago. I have: 2 Angelfish 2 Black Phantom Tetras 3 Serpae Tetras 2 Male Guppies 3 Silver Tip Tetras Along with those fish, I have a piece of driftwood and a variation of multiple plants. Parameters: Nitrate: 0.00 Nitrite: 0.00-0.5 pH: 7.00 KH: 0-40 GH: 180.... (yeah, I don't know why it's so high) Ammonia: (Not sure at this time, I do not have the testing kit right now, even though this is vital) My two angelfish have been breathing extremely heavily ever since I put them into my tank. Just starting this morning, one of them was trying to breathe air at the top of the tank. I've attempted everything I've found online in order to gain more oxygen, but this is not helping. After trying that, I thought that the GH levels were doing this to my fish, as they are extremely high. I've tried to find more research on this, but I have had no success. All my fish are breathing somewhat heavily, but nowhere near as much as much my angelfish. Is the high GH levels causing this? If so, how do I fix it? Thank you!