Dosing Ammonium Chloride in water produces ammonia plus hydrochloric acid. Dosing Ammonium Bicarbonate produces ammonia plus CO2, which means dosing ammonia and carbonic acid. This is how calcium reactors work, the CO2 pumped into the water produces carbonic acid which dissolves the dead coral media. Both of these methods of dosing ammonia will lower the pH in the aquarium. I don't know how much, but I don't like anything that lowers the pH in a coral growing aquarium. Neither method will raise phosphate, which also needs to be dosed if your nutrients go too low in an aquarium. Maybe just feed the fish and corals more and/or remove less of them via filtration/skimming/etc.