Quarantine, ich / white spot, and what makes a reef tank crash — triage, not diagnosis.
4 questions, answered honestly and water-first.
Yes — it's the single best way to keep diseases like ich and velvet out of your display, and it's non-negotiable for ich-magnets like tangs. Keep new fish in a separate, cycled tank for a few weeks to observe and treat before they join the reef. Even a basic quarantine beats none.
That salt-grain look is most likely marine ich, usually triggered by stress or a parameter or temperature swing. Move affected fish to a quarantine tank and treat properly there — many reef-safe animals can't tolerate the medications. This is general guidance, not a diagnosis; for a serious case, get an experienced reefer's or aquatic vet's eyes on it.
Usually a swing or a shock: a big parameter change, an overdose, an equipment failure (heater or return pump), overstocking, or a dead animal fouling the water. The defences are the same as good keeping — stability, not overstocking, and testing so you catch trouble early.
Watch for a change from its normal self: clamped fins, rapid breathing, flashing (scraping on rock), hiding, or not eating. The first check is always the water — test it — because most "illness" in a new tank is really water quality. Quarantine anything visibly sick and treat it away from the display.
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Short answers from the Coralkin team — kind, general guidance, not a diagnosis. When something looks wrong, test your water first, and for a serious case ask an experienced reefer or an aquatic vet.
