When I cycle a tank I use plants. I make sure that between 30-50% of the volume of the tank is in plant, switch on filter, heat, light ( 10 hours per day). Wait 10 -14 days and once the plants start growing. You can safely start adding fish a few at a time over the next few weeks. The bio load capacity of the tank will increase over time. The plants are a crucial part of the nitrogen cycle. I always use natural gravel in my tanks.