This is kind of urgent - I'm watching someone's dogs currently because that is what I am experienced in but they also have an aquarium. I have little to know experience with fish and I did warn the owners. I don't have 100% of the information, a lot of it is guesswork but I really need help.
In order to feed the fish, I dissolve krill in ice into a cup of water and distribute it. I feel so dumb, but for the first 4 or so meals, I used about 3 cups of Crystal Springs water from a water cooler to feed them. I'd say this tank is a little smaller than 125 gallons and I'm fairly sure it's saltwater because of the breeds of fish. Since then, I've fed them about 4 or 5 times just using the tank water (I feel bad for not realizing that at first, I know virtually nothing about caring for fish).
The owners come back in about 5 days, is there anything I can do to fix this? How harmful will this be to the fish? I've already noticed the gravel is dirtier than before. I also haven't been able to contact the owners because they have no cell connection where they have traveled to. Any advice would be greatly appreciated