This question has probably been asked many times, but I'm new to this forum. I have a 30 gallon tank that houses two gold fish. I have owned this tank for several years, at one time I lost all my fish which I think it was because of buying a sick fish from a place that I will not buy fish from again. The tank set empty for almost a year and I had to get it going again in a hurry! My backyard got flooded and I had to save my 2 large gold fish from being washed away. I filled it with tap water, treated it with AquaSafe, let it set for 24 hours, and then put the fish in the tank. I ended up losing one, but the larger one survived, and that was back in May. I recently bought another one for that tank it is doing well. Now for the question. Anytime I add water to that tank, I buy distilled water. I have just got a 55 gallon tank from a friend and I need to fill it up. I have not decided on the type of fish for this tank, but I want to get it ready. Do I fill it up with tap water from my house, or buy distilled water? Thanks.