Hello everyone. I am very new to this hobby and I am about to lose all of my fish. I currently have a 50 gallon tank with 4 fish (i had 5 yesterday but one sadly passed). I have been keeping up with water changes but I have been dealing with cyano for the past few weeks. On sunday, I did a normal water change but I had used salt and bottled spring water instead of the bottled saltwater I was using prior to making my own saltwater. I checked the gravity of the saltwater I had made and it was just fine but when I put it into my tank, it increased the gravity way too much. I have been decreasing the gravity little by little with bottled spring water as I do not have any RO water. (sorry for the stupidity). Is there ANYTHING I can do to save my fish? It may be a little too late to help them but if there's anything I can do to help, them please let me know. As I mentioned before, I am completely new to this and I am still in the process of learning things. I also forgot to mention, I got my fish from a family friend of mine who had to get rid of them so I do not know how old they are. I will admit I was extremely stupid for not doing more research prior to getting them but our family friend had to give them away asap. If there's anything I can do to save them, that'd be wonderful but I don't think they'll make it through the day if I don't do something asap!