Don't give up on your longnose hawkfish just yet. I have one in my reef tank for 20 months. I have a 100 gal tank with 5 shrimps, 2 cleaner, 2 scarlet/red blooded and one coral banded. They are getting along fine and stay away from each other, the shrimps I mean, provided you have plenty of rocks.
My longnose hawkfish did peck at one of my cleaner shrimps once, but it was too big for them unless yours are very very tiny where it can feed it in it's mouth. Longnose hawkfish is fine with shrimps but not other species of hawkfish. I feed mine with frozen food and chopped prawns meshed with vitamins, mussels, clams, spitulina etc. It does not take flakes and pellets.
Becareful if you want to keep a lobster in your tank, may not be suitable for a reef tank for most lobsters, they also eat small fishes. Do research on the species before you decide to buy one. Check iout at www.wetwebmedia.com, an excellent website for Q&As.
Good luck.