Marine medicine splits into three distinct categories that get treated very differently: fish disease, coral health and dipping, and pest eradication (aiptasia, cyano, unwanted hitchhikers). Keeping the right product on hand before a problem shows up matters more in a marine system than almost anywhere else in the hobby, since livestock and coral losses from a delayed response are rarely recoverable. If you’re keeping freshwater fish rather than a reef, our Freshwater Fish Disease & Medication Guide covers that side separately. This guide is marine-specific throughout.
Fish Disease Treatment
Seachem Cupramine (also in 100ml) is a copper-based treatment for marine ich and other external parasites, dosed carefully since copper is also toxic to invertebrates and corals, so it belongs in a dedicated quarantine tank, not the display. Seachem’s Poly series covers bacterial and fungal issues without copper: MetroPlex targets internal parasites and some bacterial infections, KanaPlex treats bacterial infections including fin and tail rot, and SulfaPlex and Focus round out the line. Focus in particular is often paired with the others as a binder that helps medication adhere to food for internal treatment rather than dosing the water column directly. Seachem Neoplex is a broad-spectrum antibacterial worth having as a general-purpose option when a specific diagnosis isn’t clear yet.
API Pimafix is a plant-extract-based antifungal and antibacterial treatment that’s gentler than copper-based options, making it a reasonable first response for a fish showing early signs of fin damage or fungal patches before escalating to a more targeted medication.
Coral Health and Dipping
New coral should never go straight from bag to display: a dip catches pests and stressed-coral pathogens before they reach your existing system. Tropic Marin Coral Clean and Reef Dip both serve this quarantine-dip role, and Easy Life Excital (also in 500ml) supports coral immune response and recovery after stress from shipping, fragging, or a dip itself. Tropic Marin Immuvit and Reef Actif work on ongoing coral vitality and immune support rather than acute treatment, worth dosing as a preventative rather than waiting for visible stress. Korallen-Zucht Amino Acid Fish Concentrate supports fish health and coloration broadly and is worth mentioning alongside coral-focused products since it’s frequently dosed in the same reef systems.
Pest and Nuisance Control
Aiptasia anemones are one of the most common unwanted hitchhikers in reef tanks, spreading quickly if not addressed early. Frank’s Aquarium F-Aiptasia Killer, Red Sea Aiptasia-X, and Tropic Marin Elimi-Aiptas all target aiptasia directly with an injectable or applied treatment rather than requiring manual removal, which often just fragments the anemone and makes the problem worse. For cyanobacteria outbreaks (the reddish-purple slime that spreads across sand and rock), Korallen Zucht CyanoClean targets the bacteria directly rather than relying solely on the manual siphoning and flow adjustments that often only slow an outbreak down.
Seachem Garlic Guard deserves a mention here too. It’s commonly used, more as an appetite stimulant than a medication in the strict sense, to get a fish eating again during or after a disease treatment, which is often the difference between a fish recovering and one that declines further from not eating during the critical days after treatment starts.
Quick Reference
| Problem | Product |
|---|---|
| Marine ich / external parasites | Seachem Cupramine |
| Bacterial infection / fin rot | Seachem KanaPlex, Neoplex |
| Internal parasites | Seachem MetroPlex |
| Fungal / early fin damage | API Pimafix |
| New coral quarantine dip | Tropic Marin Coral Clean, Reef Dip |
| Coral stress recovery | Easy Life Excital |
| Ongoing coral immune support | Tropic Marin Immuvit, Reef Actif |
| Aiptasia anemones | Frank’s F-Aiptasia Killer, Red Sea Aiptasia-X, Tropic Marin Elimi-Aiptas |
| Cyanobacteria outbreak | Korallen Zucht CyanoClean |
| Fish off food after treatment | Seachem Garlic Guard |
Building a Quarantine Kit Before You Need It
The single biggest mistake in marine disease management is not having medication on hand when a problem appears. By the time symptoms are visible and you’re placing an order, a parasite outbreak can already be established across every fish in the tank. A basic kit worth keeping stocked year-round: Cupramine or a Poly-series treatment for a dedicated quarantine tank, a coral dip for new arrivals, and an aiptasia treatment, since all three cover the situations most likely to come up unannounced in an established marine system.
