This page contains affiliate links.  All that means for you is that if you click on one of my links and make a purchase, I receive a small commission.  This helps me keep this content 100% free!  But rest assured, I only recommend products I know and trust! Happy Reefing!

The Beginner Guide To Saltwater Fish Medication And Treatment

Table of Contents

Disclaimer: I am NOT an expert.  I am NOT a veterinarian.  I am NOT a medical professional.  But I have spent years trying my best to compile the most accurate information available.  Saltwater hobbyist rarely agree on anything, especially when it comes to fish disease diagnosis and treatment.  Please use this guide as a starting point for your research.

Saltwater fish medication and treatment is one of the most complex topics in this hobby, and can be extremely overwhelming.  There are so many blogs and online communities that discuss every detail of this topic.  But I haven’t found one to put it all together into an easy to digest yet comprehensive guide.  That’s what this bad boy is for!

This is a really, really hard topic, and here’s why:

  • No matter what you do, your fish will often die anyway.
  • By the time you notice a problem with your fish, it is often too late.
  • Some species respond well to a certain med while others don’t.
  • Meds can kill your beneficial bacteria and inverts.
  • Until you have experience, you’ll have no baseline to know what is normal and what is not.
  • Many diseases present with similar symptoms, but require different treatments.

You get the idea.

Hands down the two best things you can do is try to prevent disease from happening and use a quarantine tank.

Enjoy the guide, and email me with any suggestions or inaccuracies.  contact@myfirstfishtank.

For a comprehensive guide to fish disease, check out the book below by Edward Noga.  It is considered the fish disease bible.

I) Common Treatments For Marine Fish Infections

This section is meant as an overview of each method.  For more detailed instructions on how to do each method, a simple Google search will yield results! And maybe I’ll write another guide in the future!

You can click on the links below to jump to that section:

1. Freshwater Dip

Freshwater dips are used to provide temporary relief from parasites.  The theory behind it is that external parasites hate hyposalinity, and will fall off the fish when exposed to freshwater for 3-5 minutes.  While your fish will not like the process, they are typically more hardy than the parasite.

Here’s the basics of how it works:

  • Fill a bucket/container with RODI or distilled water.
  • Warm the water to match your display tank.
  • Optionally, add an ammonia neutralizing product such as Kordon AmQuel and an antibiotic such as API Furan 2 to help prevent secondary infections.
  • Place your fish into the container for a period of 3-5 minutes, keeping the water moving with a turkey baster.
  • If your fish shows signs of severe distress, remove it immediately.

A freshwater dip is not really a cure for parasites, but it can help remove some of them and extend the lifespan of your fish, giving them more time to respond to an anti-parasitic medications such as Hikari PraziPro.

But if your fish is already stressed out by disease, a freshwater dip could actually have the opposite effect and lead to its death.

2. Tank Transfer Method

Here’s the thing about the tank transfer method.  It really only treats Marine Ich. So identifying the disease correctly is crucial.

The Tank Transfer Method (TTM) works by disrupting the lifecycle of of ich. Basically, by moving your fish between tanks every 72 hours, you are betting that during one of those transfers, the ich will have fallen off, but did not have enough time to spawn. That’s why sterilizing each bucket/tank in between each transfer is crucial, because you’ll be killing the ich at the bottom of the bucket in the process.

You need to have either two buckets or two quarantine tanks with separate equipment.  Two large buckets would work as long as you have a piece of pvc for hiding, a thermometer, and an air stone.

This will take 13 days, and you transfer the fish a total of four times, every 72 hours (no more than 72!). Sterilize the bucket after each transfer with either vinegar or bleach, and add new saltwater.

For a complete explanation of this method, just do a Google search by clicking HERE

3. Hyposalinity

Not to be confused with a freshwater dip, the hyposalinity method is a lengthy quarantine process whereby your fish is kept in a low-salt environment that will kill marine Ich.

Again, there is debate about this, but hyposalinity is known to work against ich, and it may work against other types of parasites as well.

Basically, the fish can withstand low salt conditions better than the parasite.

There are some incredibly detailed guides out there, but here are the basics:

  • Only use in a fish only quarantine tank, never in a reef tank or with other invertebrates.
  • Over a period of 48 hours, slowly lower the salinity of the qt to a specific gravity of 1.009
  • Start a four week clock from the first time your fish is clear of ich.
  • If at any time the ich reappears, the clock has to start over.
  • After four weeks with no ich, you can slowly raise the saltwater back to normal, but keep in qt for another four weeks.
There are way more detailed guides out there, so click HERE to find them.

A UV sterilizer is not a magic cure all, but it can help kill free floating algae, bacteria, and parasites.  

A UV sterilizer is basically a piece of tubing with a UV bulb inside.  Using a pump, water passes into and out of the UV sterilizer, coming in contact with the UV light. UV light damages the DNA of a cell, preventing it from reproducing, essentially killing it.

UV sterilizers in a marine tank are known to help reduce and kill cyanobacteria, Marine Ich, Marine Velvet, and algae spores. But I repeat, they only kill free floating organisms, so will have no effect whatsoever on any parasite attached to your fish or buried in the substrate.

There is a misconception that various species of cleaner shrimp can cure certain parasitic infections from your fish by eating them.  Some studies have shown, based on the stomach contents of cleaner shrimp, that they actually do NOT eat many parasites at all.

So the moral of this story is, if your fish is suffering from any sort of parasite (ich, velvet, flukes), a clean up crew is not the solution.

II) Saltwater Fish Medications

Alright, get ready… This is probably the longest and most confusing part for beginners and advanced aquarists alike! So here’s what we are going to do…

  • By category (parasitic, bacterial, fungal), we are going to break down the most common medications available and what they treat.
  • There are no viral medications, so we’ll skip those.

So, this section is a breakdown of medications.  If you are trying to diagnose a fish disease, check out The Beginner Guide To Saltwater Fish Disease.

Quick note: We are not endorsing any of the medications below.  We are just trying to help you understand this complex subject. 

You can click below to jump to that section.

Antiparasitics

The following medications are in alphabetical order by company. This is not an exhaustive list. Being on this list does not imply we recommend the product.

A couple terms you should probably know before going on:

  • Biofilter Safe– some medications will kill the beneficial bacteria in your tank, causing your ammonia and nitrate to spike.  If a medication is not biofilter safe, then you need to use it in a quarantine tank without live rock.
  • Reef Safe- some medications will kill invertebrates (corals, anemones, snails, crabs, you get the idea).  If a medication is not reef safe, then you need to use it in a quarantine tank without invertebrates. 
      • Active Ingredient(s): Metronidazole (antibiotic) & Praziquantel (antiparasitic).
      • Details: Gram-negative plus a parasitic.
      • Biofilter Safe? Yes.
      • Reef Safe? Not reef safe unless used with the binding agent Seachem Focus, and food.
      • What It Treats: Gill & skin flukes, swollen abdomen, velvet, and hole-in-the-head disease.
      • Active Ingredient(s): Nitrofurazone & Furazolidone.
      • Details: Broad spectrum antibiotic.
      • Biofilter Safe? No.
      • Reef Safe? No.
      • What It Treats: Internal/external bacterial & protozoan (parasitic) disease.  Also contains a slime coat.
      • Active Ingredient(s): Praziquantel.
      • Details: Anti-worm medication that prevents larvae from growing and multiplying.
      • Biofilter Safe? Yes.
      • Reef Safe? Yes.
      • What It Treats: Flukes, tapeworms, flatworms, and turbellarians.
      • Active Ingredient(s): Formalin (formaldehyde) & Malachite Green.
      • Details: A low dose of formalin (11.52%), so probably not a great treatment for Brooklynella.
      • Biofilter Safe? Relatively safe when used as directed.
      • Reef Safe? No.
      • What It Treats: Marine Ich, external protozoan, & fungal diseases.
      • Active Ingredient(s): 100% natural organic herbals.
      • Details: An all natural ich treatment, questionable efficacy when compared to other chemical ich treatments.
      • Biofilter Safe? Yes.
      • Reef Safe? Yes.
      • What It Treats: Marine ich, protozoan, and fungal infections.
      • Active Ingredient(s): Formalin & Malachite Green.
      • Details: Non antibiotic treatment. Not the recommended 37% formalin for treating brooklynella.
      • Biofilter Safe? Unknown, but formalin is known to have a negative affect on the biofilter.
      • Reef Safe? No.
      • What It Treats: Marine ich (may be ineffective), protozoan parasites, and mild fluke outbreaks.
      • Active Ingredient(s): Crystallized Peroxide Salts.
      • Details: Water conditioner used to de-pollute water. Contains reef safe oxidizing agent.
      • Biofilter Safe? Yes.
      • Reef Safe? Yes.
      • What It Treats: Marine ich, and possibly marine velvet
      • Active Ingredient(s): 5-Nitroimidazoles
      • Details: Targets Marine Ich during its infectious, free swimming stage.
      • Biofilter Safe? Yes.
      • Reef Safe? Yes.
      • What It Treats: Marine ich.
      • Active Ingredient(s): Acriflavine, Aminoacridine, & Formalin.
      • Details: Copper free, reef safe treatment for marine fish with fin rot, flukes, & parasites.
      • Biofilter Safe? Yes.
      • Reef Safe? Yes.
      • What It Treats: Fin rot, flukes, marine velvet, & brooklynella.
      • Active Ingredient(s): Copper
      • Details: The gold standard for treating marine ich and velvet.
      • Biofilter Safe? No.
      • Reef Safe? No.
      • What It Treats: Marine ich & marine velvet.
      • Active Ingredient(s): Metronidazole.
      • Details: Gram-negative antibiotic.  Can use together with Seachem Kanaplex & Seachem Focus for a more broad spectrum.
      • Biofilter Safe? Yes.
      • Reef Safe? Only when used with the binding agent Seachem Focus. You don’t want Metroplex in the water column.
      • What It Treats: Marine ich (although most hobbyists disagree)& hole in the head.
      • Active Ingredient(s): Aldehydes, Malachite Green, & Polymers.
      • Details: Employs a proprietary, synergistic blend of aldehydes, malachite green, and fish protective polymers that effectively eradicates many ectoparasites and external fungal, bacterial, and viral lesions.
      • Biofilter Safe? Yes.
      • Reef Safe? No
      • What It Treats: Ectoparasites (ich, velvet), fin rot, flukes, external fungal & bacterial lesions.

Antibacterials

To fully understand why there are so many different types of antibiotics, we need to discuss Gram staining.

Gram Staining

Developed in 1882 by Danish bacteriologist Hans Christian Gram, Gram staining helps to differentiate between different types of bacteria based on whether or not the cell accepts a purple dye.

Those bacteria that do accept the dye are known as Gram positive, and those that don’t are known as Gram negative.

So different types of antibiotics are more effective against different types of bacterial infections (this is complicated, I know!).

Gram negative infections are the most common in saltwater fish.  But most nitrifying bacteria are also Gram negative, which means using a Gram negative antibiotic can hurt or kill of your biological filter.

Categories of Antibiotics

Most antibiotics can be classified into one of three categories:

  • Gram positive
  • Gram negative
  • Broad spectrum

Especially for beginners, a broad spectrum antibiotic is usually recommended because it has the greatest chance of treating the most bacterial infections.

Common Antibiotic Medications

The following medications are in alphabetical order by company. This is not an exhaustive list. Being on this list does not imply we recommend the product.

      • Active Ingredient(s): Erythromycin.
      • Details: Broad spectrum, but more so Gram positive.
      • Biofilter Safe? Yes in moderation.
      • Reef Safe? Yes in moderation.
      • What It Treats: Fin/tail rot, open wounds, body fungus, gill disease, popeye & cyanobacteria.
      • Active Ingredient(s): Nitrofurazone.
      • Details: Broad specturm.
      • Biofilter Safe? No
      • Reef Safe? Probably not.
      • What It Treats: Open red sores, gill disease, fin & tail rot, cloudy eyes, mouth fungus, dropsy.
      • Active Ingredient(s): Metronidazole (antibiotic) & Praziquantel (antiparasitic).
      • Details: Gram-negative plus a parasitic.
      • Biofilter Safe? Yes.
      • Reef Safe? Not reef safe unless used with the binding agent Seachem Focus, and food.
      • What It Treats: Gill & skin flukes, swollen abdomen, velvet, and hole-in-the-head disease.
      • Active Ingredient(s): Melaleuca. 
      • Details: All natural tea tree oil, broad spectrum, homeopathic. Can be combined with API Pimafix.
      • Biofilter Safe? Yes.
      • Reef Safe? Yes
      • What It Treats: Open wounds, abrasions, fin/tail rot, cloudy eye, mouth fungus, and promotes regrowth of damaged fins and tissues.
      • Active Ingredient(s): Pimenta Racemosa. 
      • Details: Broad spectrum bay rum oil. Primarily an antifungal with minimal antibiotic properties.  Melafix is better for bacterial infections, but you can combine the two together.
      • Biofilter Safe? Yes.
      • Reef Safe? Yes
      • What It Treats: fungal infections on body and fins.
      • Active Ingredient(s): Nitrofurazone & Furazolidone.
      • Details: Broad spectrum antibiotic.
      • Biofilter Safe? No.
      • Reef Safe? No.
      • What It Treats: Internal/external bacterial & protozoan (parasitic) disease.  Also contains a slime coat.
      • Active Ingredient(s): Erythromycin.
      • Details: Broad spectrum but more so Gram positive.
      • Biofilter Safe? Yes in moderation.
      • Reef Safe? Yes in moderation.
      • What It Treats: Fin/tail rot, open wounds, body fungus, gill disease, popeye & cyanobacteria.
      • Active Ingredient(s): Minocycline.
      • Details: Broad spectrum.
      • Biofilter Safe? Yes with caution.
      • Reef Safe? Yes, with caution.
      • What It Treats: Fin/tail rot, popeye, dropsy, internal & external infections.
      • Active Ingredient(s): Polymer bound nitrofurantoin.
      • Details: Acts as a binding agent & meant to be mixed with other medications and food to treat internal infections.
      • What It Treats: Depends on what antibiotics it is combined with.
      • Active Ingredient(s): Kanamycin.
      • Details: Broad spectrum.
      • Biofilter Safe? Yes.
      • Reef Safe? Yes in moderation.
      • What It Treats: Fin/tail rot, dropsy, popeye. Can be combined with Seachem Metroplex & Seachem Focus
      • Active Ingredient(s): Metronidazole.
      • Details: Gram-negative antibiotic.  Can use together with Seachem Kanaplex & Seachem Focus for a more broad spectrum.
      • Biofilter Safe? Yes.
      • Reef Safe? Only when used with the binding agent Seachem Focus. You don’t want Metro in the water column.
      • What It Treats: Marine ich (although most hobbyists disagree)& hole in the head.
      • Active Ingredient(s): Neomycin Sulfate.
      • Details: Broad spectrum.
      • Biofilter Safe? Yes with caution.
      • Reef Safe? With caution. Tolerated by most invertebrates, although may stress delicate species.
      • What It Treats: Most external infections such as fin/tail rot, bacterial lesions, bloat, & mouth rot.

Antifungals

The following medications are in alphabetical order by company. This is not an exhaustive list. Being on this list does not imply we recommend the product.

      • Active Ingredient(s): Melaleuca. 
      • Details: All natural tea tree oil, broad spectrum, homeopathic. Can be combined with API Pimafix.
      • Biofilter Safe? Yes.
      • Reef Safe? Yes
      • What It Treats: Open wounds, abrasions, fin/tail rot, cloudy eye, mouth fungus, and promotes regrowth of damaged fins and tissues.
      • Active Ingredient(s): Pimenta Racemosa. 
      • Details: Broad spectrum bay rum oil. Primarily an antifungal with minimal antibiotic properties.  Melafix is better for bacterial infections.  Can be combined with API Melafix.
      • Biofilter Safe? Yes.
      • Reef Safe? Yes
      • What It Treats: Fungal infections on body and fins.
      • Active Ingredient(s): Chloride salt
      • Details: More harsh than Kordon Methylene Blue. Often combined with formalin.
      • Biofilter Safe? Yes, when concentrations don’t exceed 0.1 ppm.
      • Reef Safe? No
      • What It Treats: Marine ich, velvet, & fungal infections.
      • Active Ingredient(s): Chloride salt.
      • Details: Better tolerated than Kordon Malachite Green.
      • Biofilter Safe? No.
      • Reef Safe? No.
      • What It Treats: Various fungal infections.