I'd skip the chromis in a smaller tank. Even if you got 6 they'd probably kill each other off until there was only 1-2 left. I'd go for 5-6 fish max. So the gramma, clowns and fire fish would be fine. You could add 1-2 more small fish as well imo
with that stocking.
Oh and aqadvisor is not a good site for Sw
stocking. There's so many factors other than just bio load that go into Sw
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