I am starting a new 50 gallon and I fillied it with RO from lfs. I have read that you need to add minerals back to RO is this true? Also I took my sponge from my established 15 and put it in my new cartridge and also shook my other filter media inside the new tank. It has been about 4 days and still no drop in ammo. Is this normal or because of 100% RO WATER? Should I drain some water and add tap water? Also I didn't add prime, should I ? Thanks for advice