The original Aquasoil Amazona used to leach a lot of ammonia in the first few weeks in the tank. So, the correct way to use it was to change 50%+ of the water every few days at first, then weekly until it stopped leaching so much. You shouldn't wash it first, and it is intended to be used alone, without a cap. ADA likes to persuade you to use their "little white balls" under the substrate, but it works fine without it. It does contain less potassium than the plants need, so they recommend using their "brighty green" (or something like that) to supplement the missing potassium, but if you just dose the water per the EI method it also works fine. And, Amano recommended replacing it every year or so, because the nutrients don't last forever. But, I'm still using mine, after about 2 years.