well crushed coral isnt realy the best substrate. it would be fien for a FO, but i wouldnt even recomend it for a reef.
for filtration, id jsut get a protein skimmer, some powerheads, and a HOB filter for some carbon use.
and i dont think i would just hunt for "durable" fish. IMHO, if you have to realy look for special fish that will survive all, then your tank may not be ready. because although a damsel will probaly survive situations that a more sensitive fish may not, you coudl still be putting the damsel in a toxic environment. like when so many people cycle with damsels. often, their gills can burn from the amonia and never be corrected.