Nitrate is not coral food. Not even close. Coral and zoox will need to get their nitrogen from ammonia/ammonium and through bacteria that they can catch in their slime coats, if any - some corals can catch some food, but most acropora are not really good at this. This mostly mean that zoox get their nitrogen from ammonia/ammonium.
Just a trace of nitrate is all that corals need, but more might not hurt depending on what coral/type/individual. My sand bed and rock keep mine constantly around .1 nitrate, which is just enough to keep everything moving forward and is not growth limiting.
Food waste should be addressed, but keep your fish well fed for happy corals. It is OK to have some waste for your shrimp, crabs, etc to eat since they won't be happy just eating fish poop, but this should not be excessive either.
Microalgae can use nitrate directly. Most don't want this. Macroalgae can also get nitrogen from ammonia/ammonium, so there really isn't any need to get nitrate up to lower phosphates with a fuge, either. Just a trace of nitrate is fine. If you have dinos or cyano issue, then raising nitrate can growth limit these on the high end, along with higher phosphates - this is a different type of discussion since it has nothing to do with getting building blocks to corals.