Sea Hare

The Spotted Sea Hare (Aplysia dactylomela) is a large, soft-bodied algae-grazing slug bought to clear a hair-algae outbreak fast — a single one can mow a tank down in days. Treat it as a temporary tool, not a permanent resident: once the wild algae is gone it must be hand-fed nori/macroalgae daily or it starves, so plan to rehome it when the job is done. Its real danger is chemical — when stressed, predated or dying it releases a toxic ink that can crash an entire closed system, so keep activated carbon on hand and remove it promptly if it fails.