My sister passed her old tank onto me. It is a big tank. I am not sure the size so I asked a few people and they don't know either. They are guessing around 50-55 gallons. Is there any way I can find out the size? I need to know so when I set it up, I will know what dosage of stress coat to put it, what filter to use, how many fish I can put in, and all the important things to keep it maintained and balenced. I am getting mixed ideas on what to do with the tank. I can't set it up yet until I switch rooms and then I will be able to put it in my new room and start. I bought a filter for it that covers tank sizes 45-65 gallons. I am guessing it is around that size. The filter is a QuietFlow55. It's the same brand of my Quietflow10 which I have on my 10 gallon tank. I am making this topic for many reasons. To figure out the tank size and how to take good care of it and some suggestions on what to do. I have many questions so I hope you are prepared to answer them if you know what I can do. I will need a list on things that I will need for it. I am probably going to buy a new test kit that is more accurate than the one I have. I asked my friend if he think I should use sand in my tank but he said not inless if I want a saltwater tank because apparently, sand has salt in it. Is this true that if I put salt in a freshwater tank, it will turn into a saltwater tank? I want Corydoras in the tank in the future and I learned that they need a sand substrate. Will I have any problems adding big rocks in the tank? I have one that I am going to clean off if I can use it. My 10 gallon tank has 4 danios. 2 zebra and 2 leopard. The water is foggy and dirty. I did a few water changes but it's still the same. I will probably end up adding them to the bigger tank after it is set up and then empty the 10 gallon and start it all over because the tank is a mess. Will I be able to switch them back to 10 gallon after it is set back up?