For softies it's definitely not a requirement. For lps, it depends. I kept euphyllia and softies in a 20long low tech reef for 3 years with nothing but a hang on back filter, a black box led and weekly 5 gallon water changes. It didn't grow too much (may have been the xenia infestation that took over the tank) but it was healthy. The dosing pump mainly helps with stability, which is mainly an sps requirement.
BTW, don't buy Xenia, green star polyps, or anthellia. You'll like that they're easy to grow at the beginning. You'll hate them at the end.