I'm not getting the fish just to cycle a tank. I plan to keep it.
You could use the goldfish yes but it's still better to cycle without fish so you don't needlessly stress the fish out.I don't have an established aquarium. The tank is 36 gallons.
It'll depend, hence the test kit. For mine, a single 2" goldfish in a 10 gallon, I had to do at least 30% daily, sometimes 2 30's or a 50. Depended on how much the test read. If it was between 0.25 and 0.5, a 30 took care of it. If it was at 0.5, that means you need to reduce it by half, so a 50%How much water change? (percentage)