I have a 30 gallon with sump and have a black clown goby, mimic tang, pair of mandarins, pink spot goby and a midas Blenny , lots of shrimp and coral but the tank is also over 3 years old and only added fish very slowly. You just need to maintain parameters, good water quality and enough room to swim and hide are key, you'll find your sweet spot just give it time
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