To have someone come in with a 210, running a calcium reactor, corals, plenty of nice fish ect. Not know how much light they have, what kind or how many powerheads. What kind of lights be it pc, t-5, mh. How to change any of the bulbs to boot. Also have no clue what Ich is until half of the fish are gone. Not knowing what RODI is. I don't agree with being abrupt or short, I learned to ask a million questions. If not you miss important things like leaving your lights on 24/7 may cause cyano. Topping off with saltwater may change your salinity ect.