While Fabuloso can be a great cleaner on its own, when mixed with certain other products, it can create toxic fumes or cause damage to surfaces.
Cleaning your toilet tank often helps to prevent mold, rust, and mildew from developing that can discolor your tank's interior and lead to metal corrosion overtime from some of the tank's parts.
You should never mix any other cleaners with bleach, since bleach can produce potentially fatal compounds when combined with other chemicals.