converting to a saltwater tank

Question
Hi Jennifer, I have a 35 gallon freshwater aquarium that I would like to convert to a saltwater tank.  The three freshwater puffer fish that are presently in it will be moved to a little smaller tank because I really want to try out a marine tank.  Can I do this without draining all of the water? Can I just add salt to the water that is already in it? I know nothing about saltwater tanks but am ready to learn.  An info you can give me regarding this would be most helpful.  The tank is a hexagon so it is taller than it is wide will this effect the types of fish I can put in the tank? (my condo has limited space so this tank will have to do for now!)Do they require special lighting? Will the filter I have on my freshwater tank work with the saltwater tank? I would like some live rock as well ... thanks alot for your help!

Answer
Hello Courtney. Converting a freshwater tank to salt water is quite easy. You will need to drain all the water out and change the gravel to a crushed coral or live sand type. One that is specifically used for salt water. These are designed to help buffer your water and keep your pH stable. Buy some high quality sea salt mix(one designed for a saltwater tank)and mix it with a high quality water like RODI(reverse osmosis deionized) water or distilled at a rate of about 1/2 cup per gallon. As for the size of your tank the answer is yes it being taller than it is wide will effect the carrying capacity(amount of fish you can house) of the tank. Keep the number of fish a little lower than you would a rectangular 35 gallon tank. Lighting for a salt water tank will mostly depend on what you want to put in it. If you plan to have a fish only tank than your regular lighting may due.(although it won't show off your tank as nicely as those designed for saltwater do) If you are planning on live rock than you may want to research a better lighting system. Power compacts will do at a rate of about 3-5 watts per gallon. I recommend keeping a fish only tank and mastering that before you move on to invertebrates. The filter may be fine but I do not know how old it is or what kind so I couldn't really tell you much about that.There is a book on the market called "the marine aquarium problem solver" and it is a good book to get you started.