You really shouldn't add that many fish all at one time. How long has your aquarium been set up and running? Are there already fish in the tank? If you're going to be adding 30 fish all at once I would highly recommend using either Seachem Stability or Aquavitro Seed for a week or two after adding the fish to help boost the beneficial bacteria. I would also recommend using Seachem Prime as a water conditioner to help keep the ammonia and nitrates under control. Welcome to the forum.