[Delphinus]

Monitpora capricornis is pretty forgiving. Pocillopora is also a nice one that I don't think is terribly demanding.

Also some acros aren't too fussy (although it's more an exception I think, than the rule). I have an A. valida (looks like one anyhow) that has lived through everything I could throw at it, and seems to grow (and have ool colour) no matter what the Ca/Alk levels are.

That said most acros, I find, seem to be either "growing" or "dying". I.e., if the levels aren't perfect for optimal growth, the colony is at risk of crashing, because there's no middle ground (or if there is, it's a very narrow tolerance). Just something to keep in mind before you suddenly get an SPS bug or something like that; the more you have, the higher the draw, and thus the closer you need to watch the levels.