| The best bet for you to do is to continue feeding your tank as if the goldfish and snail are still in the tank. This will add food which will deteriate and feed the bacteria colony. You can also get one of a few products such as "Cycle", "Bio Spira", or "Bact-Seed" (and its sister product "Bact-Feed) to help put the bacteria you need right into the tank. These will help you out immensly when you are doing water changes, which you still should do to help avoid or minimize algea growth. Keep in mind that you may want some algea for your snail, but it is better to not let it accumulate too much as your snail may not be fond of the types of algea you will grow during the cycle period.
You are well on your way to having a cycled tank. Your nitrates are not going to be a stable chemical until your tank is fully cycled. The best bet is to keep monitoring the nitrites and watch them go down over time. Then you will see everything level out with ammonia and nitrites near 0 and nitrates at very low levels (less than 0.3 ppm).
I think you were wise to get the fish out of the tank for their health. Now you just need to get the bacteria colony big and strong. You can do this easily by feeding the tank without fish and once a week vaccuming out the gravel or substrate to get the majority of the food that is just rotting away so that the tank does not look bad or smell bad. | 
