Ammonia (NH₃) and Ammonium (NH₄) always exist in an equilibrium based on mostly pH in water. So regardless of adding ammonia or ammonium you will be "adding both" every time and there is no "safer" or "less harmful" way to do it. When you look at the small amounts being added by Randy's suggestions it becomes apparent why it isn't dangerous to fish or corals though. People often have a wrong idea of how much total ammonia (NH₃ + NH₄) you actually need to reach dangerous ammonia (NH₃) levels in a reef tank.
In our reef tanks with a pH around 8 the equilibrium is very far on the side of ammonium (NH₄), so something like 93% of the total ammonia (NH₃ + NH₄) is ammonium (NH₄) and only 7% is ammonia (NH₃). Theoretically it doesn't even matter if you start bubbling pure ammonia gas into the tank, the equilibrium would ensure 93% of it becomes ammonium as long (as the pH doesn't drop).
Scientific papers often use a different method of measuring ammonia and that's probably why people started to believe small amounts like 0.1ppm or 0.2ppm would already be dangerous, when in fact there still is a lot of headroom until you would cause any detectable damage.
You start by adding something like 0.1ppm total ammonia (NH₃ + NH₄) which is completely safe when ammonia is currently undetectable. You do so every x hours and if you see ammonia accumulating (so your test actually starts to detect something), you know there is more than enough nitrogen in your system and you don't even need to dose that much (or anything).
Ammonia is taken up very rapidly and your tests won't detect any ammonia accumulating when the tank is actually "nitrogen starved".
If you had more animals in your tank that would increase nitrate to detectable levels they would also release ammonia so dosing it is not more dangerous than having more animals in the tank as long as you do it in small portions
Oh, and also Mr. Mojo is right, I think we need more info before we can even say if nitrogen depletion is an actual issue in your tank.
