I know plenty of stunning SPS tanks that run nitrate over 20ppm, but it's not the issue.
The REAL issue is where the SPS came from. Many commercial fraggers keep their frags in low nutrient tanks because they are less maintenance. Virtually all SPS including acropora can acclimate to > 20 nitrate levels, but over an extended period of time. If you put that same frag in a 24ppm tank (yours) and it comes from a tank with barely 1ppm of nitrate you *will* have issues ,especially with acros or more sensitive SPS. This is why I often test the water the frag comes in to see what the coral is used to. If there's a massive difference in nutrient levels then you should quarantine the frag in a tank with intermediate nutrient levels. Corals can acclimate quickly between tanks with different calcium levels and alk levels provided they are within reason. A 20 point jump in nitrate through combined with having to adjust to different lighting causes 90% of new SPS acclimation issues.
In fact, if you are spending some money on frags from a single source I would insist on knowing their params. If their tanks have 0 nitrate...yeah...you will have issues putting them in yours. I guarantee it.
For mixed reef I feel more comfortable running nitrate at 5-10 ish because you have wiggle room both ways. You can get away with higher *if* it's stable higher and corals are used to it.
Stupid nitrate trick: if you have sump get a jar of bio pellets, put them in a media bag and throw them in your sump. You do not need a reactor - just a gimmick. They take a few weeks to ramp up, but once they do a pound of biopellets will crush nitrate.