Hey there seaworldfan...Welcome to Aquaria Central...
Ok, to start off with, the spotted hawkfish should not be put in a tank with any fish that are smaller than it, they are known to be aggressive towards smaller fish and it will go for small shrimps aswell...
I would probably choose a different fish to give you a little more choice due to the size of the tank...
See this list for fish that can be kept in 30 gal tanks..
Basslets
Royal Gramma (Gramma loreto) Length: 3", Minimum Tank Size: 20 gallon
Chalk Basslet (Serranus tortugarum) Length: 3", Minimum Tank Size: 20 gallon
Blennies
Bicolor Blenny (Ecsenius bicolor) Length: 4", Minimum Tank Size: 29 gallon
Black and Yellow Blenny (Ecsenius lividanalis) Length: 2", Minimum Tank Size: 15 gallon
Two Spot Blenny (Ecsenius stigmatura) Length: 2-1/2", Minimum Tank Size: 15 gallon
Two Spot Bimaculatus Blenny (Ecsenius bimaculatus) Length: 1-1/2", Minimum Tank Size: 15 gallon
Cardinalfish
Bangai Cardinal (Pterapogon kauderni) Length: 3", Minimum Tank Size: 29 gallon
Flame Cardinal (Apogon sp.) Length: 4", Minimum Tank Size: 29 gallon
Pajama Cardinal (Sphaeramia nematoptera) Length: 3", Minimum Tank Size: 29 gallon
Clownfish
Percula Clownfish (Amphiprion percula) Length: 3", Minimum Tank Size: 10 gallon
Ocellaris Clownfish (Amphiprion ocellaris) Length: 3", Minimum Tank Size: 10 gallon
Pink Skunk Clownfish (Amphiprion perideraion) Length: 4", Minimum Tank Size: 20 gallon
Tomato Clownfish (Amphiprion frenatus) Length: 5", Minimum Tank Size: 20 gallon
Damselfish
Yellowtail Damsel (Chrysiptera parasema) Length: 3"
Blue Damsel (Chrysiptera cyanea) Length: 2"
Talbot's Damsel (Chrysiptera talboti) Length: 3"
Azure Damsel (Chrysiptera hemicyanea) Length: 4"
Blue Sapphire Damsel ( Chrysiptera sp.) Length: 3-1/2"
Tuxedo Damsel (Chrysiptera tricincta) Length: 3"
Two Stripe Damsel (Dascyllus reticulatus) Length: 4"
Three Stripe Damsel (Dascyllus aruanus) Length: 4"
Four Stripe Damsel (Dascyllus melanurus) Length: 4"
Dartfish
Orange Firefish (Nemateleotris magnifica) Length: 3"
Purple Firefish (Nemateleotris decora) Length: 3"
Gobies
Clown Gobies
-Yellow (Gobiodon okinawae) Length: 1-1/2”
-Green (Gobiodon atrangulatus) Length: 1-1/2”
-Citrinis (Gobiodon citrinis) Length: 2”
-Brown (Gobiodon sp) Length: 1-1/2”
-Black (Gobiodon strangulates) Length: 1-1/2”
-Panda (Paragobius lacunicolus) Length: 1-1/2”
Blue Neon Goby (Elacatinus oceanops) Length: 2”
Golden Neon Goby (Elacatinus sp.) Length: 3”
Greenbanded Goby (Elacatinus multifasciatus) Length: 2”
Red Head Goby (Elacatinus puncticulatus) Length: 2”
Trimma Goby (Trimma sp.) Length: 1”
Red Striped Goby (Trimma cana) Length: 1”
Yellow Watchman Goby (Cryptcentrus cinctus) Length: 3”
Orange Stripe Prawn Goby (Amblyeleotris randalli) Length: 3-1/2”
Hi Fin Red Banded Goby (Stonogobiops nematodes) Length: 1-1/2”
Two Spot Goby (Signigobius biocellatus) Length: 3”
Hawkfish
Falco Hawkfish (Cirrhitichty falco) Length: 3”
Flame Hawkfish (Neocirrhitus armatus) Length: 4”
Longnose Hawkfish (Oxycirrhites typus) Length: 5”
Pseudochromis
Fridman’s Pseudochromis (Pseudochomris fridmani) Length: 3”
Neon Pseudochromis (Pseudochromis aldabraensis) Length: 4”
Bicolor Pseudochromis (Pseudochromis paccagnellae) Length: 2”
Springer’s Pseudochromis (Pseudochromis springeri) Length: 3-1/2”
Wrasses
Sixline Wrasse (Pseudocheillinus hexataenia) Length: 3”
Carpenter’s Flasher Wrasse (Paracheillinus carpenteri) Length: 3”
Yellow Fin Fairy Wrasse (Cirrhilabrus flavidorsalis) Length: 3”
Exquisite Wrasse (Cirrhilabrus exquisitus) Length: 4”
Corals really depend on the fish you choose or want to keep..You have to check the fish's compatibility first...
Niko
