Even if they are juvenile, you need to get rid of the hippo tangs right now!!!
Once you get rid of the hippo tangs, you can get a yellow watchman goby, a clown goby, a chalk bass, a fire goby, or a bunch of other fish. Just some first ideas
90 Gallon Reef - 3 Blue-Green Chromis, 2 Ocellaris Clowns, 1 Kole Tang, 1 Midas Blenny, 1 Longnose Hawkfish, 1 Zebra Dartfish, 1 Algae Blenny, 1 Six-Line Wrasse
29 Biocube Reef - 1 Chalk Bass, 2 Black and White Clownfish, 1 Yellow Watchman Goby, 1 Fire Goby