🐠 Case Study: Why Is Finn Covered in Salt?

Meet Finn, a 4-year-old clownfish in a 90-gallon reef tank. His owner rushes in after noticing a dusting of white spots across his body and fins overnight. Finn is scratching frantically against the live rock.

The owner just added two new tangs three weeks ago. No quarantine.

You recognize this immediately: Cryptocaryon irritans, marine ich. A ciliate parasite that burrows under the epithelium, feeds on host tissue, and explodes in population when a naive fish enters the system.

Here is the problem. This is a reef tank. Copper sulfate, your gold standard treatment, would wipe out every invertebrate and coral in the system.

Your plan: move Finn and the tangs to a bare hospital tank, begin copper treatment at 0.20 mg/L free copper for 28 days, and leave the display tank completely fishless for eight weeks.

Without a host, every theront that hatches will die.

The reef survives. Finn survives. But only because of patience.

💡 The takeaway: In reef tanks, the fallow period is your most powerful treatment tool.

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