Fish To Be Avoided: (fish with incredibly low survivability in aquaria)
Moorish idol
Regal angelfish
Rock beauty
Bicolor angelfish
Genicanthus sp. angelfish
Centropyge multifasciatus
Holacanthus venusta
Most Anthias
Clown tang
Clown sweetlips
Pinatus and tiger teira batfish (batavianus)
Orange spotted filefish
Most butterlyfish (except those listed below)
Ribbon eels
Cleaner wrasses
Twinspot goby
Sleeper gobies (Valenciennea sp.)
Tilefish
Rays
Bicolor parrotfish
Princess parrotfish
Blue and Red parrotfish
Grunts
Anampses spp. wrasses
Leopard wrasses (Macropharyngodon spp.)
Pseodojuloides wrasses
Tassled filefish
Jacks
Drums
Trumpetfish
Remoras
Chambered nautilus
Fish Best Left For Experienced Hobbyists:
(finicky nature, parasite prone, specialty feeders, require specialty tanks or threatened species)
Catalina gobies (coldwater species)
Garibaldi (coldwater species and protected)
Trunkfish (box and cowfish)
Clown and Gumdrop gobies (once established a good surviver with less boisterous fish)
Radiata lionfish
Fu manchu lion
Dwarf zebra lion
Anglerfish
Mandarin dragonet (requires large amounts of live food typically)
Most large angels (require large aquariums and often specialized feeders)
Lamarck’s angelfish
Acanthurus sp. tangs (ich prone)
Kole tang (ich prone)
Chevron tang (ich prone)
Most other tangs except Zebrasoma and Naso sp. (ich prone)
All butterflyfish (except vagabond, longnose, Heniochus, golden, pebbled, Klein’s, lemon, auriga and racoon, which need large tanks)
Sea horses
Seadragons
Pipefish
All anthias
Blue chromis
Wild-caught Bangaii cardinalfish (threatened)
Longnose hawkfish (jumper)
Octopus
Cuttlefish
Porcupine pufferfish (very disease prone)
Fairy wrasses (Paracheilinus and Cirrilabrus spp.)
Dragon wrasse
Red coris wrasse
Red sailfin blenny
Striped blenny
Scooter blenny
Sandhopper
Jawfish (require tanks set up with their needs in mind)
Undulated triggerfish (unless housed by themselves)
Convict tang (very aggressive)
Fish That Require Huge Aquariums (200 gallons or more):
Sharks (require much larger than 200 gal., Nurse sharks can grow to 14ft. long!)
Most groupers (especially panther groupers)
Parrotfish
Snappers
Naso spp. tangs (however, they can be slow growers)
Moray eels (large species)
Garden eels
Soldierfish
Orbi and spade batfish
Twinspot wrasse (Coris aygula) (beginners take special note of this one)
Flounder
Venomous Species:
Stonefish (can be deadly)
Lionfish
Rabbitfish
Scorpionfish
Coral cats
Bluering Octopus (can be deadly)
Inverts To Be Avoided Or Better Left To Experts:
Non-photosynyhetic corals and gorgonids (sun polyps, carnation, devils hand, etc.)
Christmas tree worms
Goniopora sp.
Feather stars
Basket stars
Crown of thorns (duh
)
Linkia stars (poor survival until acclimated)
Many wild small-polyped scleractinian corals that are not frags
Sea apples
Sea pens
Giant Xenia
Sea slugs and nudibranchs (very few exceptions)
Flame scallop
Anemones (see below)
Bright yellow anemones {dyed; most anemones have no business being in reef aquariums and should be placed in specialty tanks)
Harlequin, clown shrimp (specialty diets)
Camel, mechanical shrimp (not for reefs)
Elegance coral (recent poor survival)
Red serpent starfish
Tubipora musica (organ pipe, usually hacked off from a larger colony)
Made a few quick changes, if a moderator happens across this please replace the original list with this should you be so inclined.