It's a 40 gallon tank. 0 Nitrites, 0 Nitrates, ph 8 (always has been for them), very hard water(always has been for them), Chlorine 0, ammonia 0. I'm down to two goldfish. The others have all succumbed in less than 12 hours. I've added extra airstones, some aquarium salt, and Microbe-Lift. I've...