Question, are both the yellow watchman and orange prawn goby sand sifters and the type of goby that will pair with a shrimp? Definitely would like to get one of those if possible.Hopefully these suggestions help you out a bit.
Blue Hippo Tang - I’d pass on the Blue Hippo until you upgrade as it will grow pretty quickly fed right. This is mainly because of its aggression in smaller tanks especially at feeding time. If you do decide to add it watch for its aggression and add as one of the last fish, not THE last fish lol as some say.
Zebrazoma Yellow/WTKT - Everyone loves a Yellow. Do you plan on going down the CB Biota road or Hawaiian WC? The WT Kole being a bristletooth is one of the more docile tangs so that’s a plus. Make sure to feed nori at least twice a day and some cucumbers and other veggie treats along the way. I fed my tangs spinach on the clip next to the nori so they don’t get picky. The Yellow will outgrow your tank eventually but much slower than the Hippo. Once he gets too aggressive or starts pushing that 4” mark I’d plan on upgrading his tank. The Bristletooth can stay in that sized tank much longer as they are the only Tang’s that can suit a 4 footer comfortably for the long part. Once he does start getting aggressively dominant be best to upgrade.
Halichoeres melasmapomus - Personally appreciate you are giving some love to this Halichoeres. Make sure to have at least an inch of sand bed for them to sleep in at night. Halichoeres are great because they eat all kinds of pests especially flatworms and monti eating nudis. He can get a bit of an attitude as he gets older. Something beneficial is add live copepods to the tank so he has at his disposal some natural food.
Banded Snake Eel- My man @Slocke keeps a few of them and even wrote an article about them you can find on here. He is your go to guy for all you need to know about these eels. Some of the best eels and super peaceful. Safest eels for fish that like to sleep in the sand at night and fish that like to burrow. And they have very tiny teeth so if they bite it hardly hurts or breaks skin, it would feel more like pressure. Plenty of meaty foods for this guy crab mussels maybe some live shrimp.
Hawkfish - IMO get a Longnose as Flame’s are a bit overrated in my opinion lol.
Since you do plan on an eel, gobies aren’t the best match up with them as they are generally small and are in the sand or on the sand most of the time. Theres the Yellow Watchman for a choice or the Orange Banded Prawn Goby. These guys would be I think your best bet. Wouldn’t recommend the other shrimp or prawn or nano gobies.
Genicanthus watanabei - Genicanthus angelfish are known to be the only true reef safe angelfish and stay on the smaller side so really good candidates for reefs. They do come with a bit of a price tag so don’t be shocked if you see them for $300 plus. I’d suggest a pair as you get the best character out of them.
I hope this helps lol. I’ll be following I want to see more!