There are clearly a lot of questions regarding aquarium water chemistry, testing, nitrogen cycle, fish stocking etc, etc that need to be addressed here...And that's okay, there are a lot of great articles online to learn all of the stuff you need to know in this hobby so I won't try to summarize them all here...To answer your question, the bacteria in your tank will last a long time without food, even looked her now that your dead snails are providing food for them, don't rush out to get fish to keep the cycle, if you're really worried about it feed them once a week or two with a small piece of food/flake/pellet or a drop or two of clear ammonia...After that, every forum has newbie threads, this one has a particularly good sticky with links to a lot of great articles, read them all, multiple times, in fact I have the page open on my desktop now I read them all the time and I've been reefing for more than a year, I'm no veteran by any means but further from rookie than most