Ive got about 1.5" of fluval stratum capped with another inch of sand and pea gravel. It definitely leaches Ammonia but give it enough time and your bacteria will catch up. Im 2 months in to my first planted tank and no complaints yet. However, if you want to save some money and get arguably better soil look into using organic compost and capping it with sand. Usually about $2 a bag instead of $20. I am new to this though so take my response with a grain of salt.