"I have better success with new fish survival when using Kordon Fish Protector. I include the product in the quarantine tank before introducing the fish. I can use it with most ich medications, if necessary. It does not cloud the water. It also seems to help to use it in the aquarium right after a cleaning/water change. The larger bottle is the most economical choice since I'm now using Fish Protector at least once a week on all my tanks. I have to admit that since I started using Fish Protector over the last few month, I've not experienced any "mystery deaths" in any of my established aquariums. Not sure it if is simply good fortune at the moment, or if the product is helping the fish to stay healthier. I'm hoping it is the latter."