A healthy Hawkfish:

Photo from the Reef2Reef Archives

Before I start this article, I want to make a couple of points. First, we have in our forum, an excellent area for the discussion of fish disease, treatment, and diagnosis. Our venerable Humblefish even created a “sticky” thread (one that stays permanently on top) called, “Medications to Keep on Hand.” So, if you have a sick fish, and you don’t know what ailment you’re dealing with, then by all means, ask questions there.

But here I want to start with prevention. I’m going to talk about when you should separate fish, why you should do this, what chemicals are useful for sterilizing and how to get them. Next time, we'll talk about medicine for the sick fish. So, let’s get started.

1. Quarantine Tank: I’m a great believer in quarantine. We’ll discuss this at length in another article, but you really need a quarantine tank. There are very few medications that are safe for both fish and invertebrates, so it’s rare that you can dose medicine inside your display tank. That means if you have a sick fish, you need a place to treat that fish separate from and away from all your treasured corals and shrimp and anemones and crabs. You might also want to think about this before you set up your tank. By that I mean, can you take apart your rock formations in your display tank if you have to catch a sick fish?

You want to do everything you can to avoid having a sick fish, and your best bet is to start with quarantine. A quarantine tank (Qtank) can double as a hospital tank (Htank), provided that you sterilize it between uses. Or you can have two extra tanks besides your display masterpiece.

A Hospital Tank

Photo from the Reef2Reef Archives
2. Two Extra Tanks: There are some really good reasons to have two extra tanks. A) Sometimes when you add several fish, it’s important to add them at the same time, and your Qtank may not be big enough to quarantine all of them. B) Sometimes you may have a fish or more in quarantine when you have another fish from your display tank (Dtank) that gets sick and needs treatment—the sick fish goes into the second tank because different diseases/treatments require different medications. C) There is a specific treatment for saltwater ich or Marine White Spot Disease (Cryptocaryon irritans) called the Tank Transfer Method. Cryptocaryon irritans is a protozoan parasite that is sadly common in ornamental marine fish. The Tank Transfer Method (TTM) requires two separate tanks.

Now keep in mind that when I say “two tanks,” they don’t have to be two fancy 50-gallon things. They can be two buckets or two simple 10-gallon bottom-of-the-line glass tanks. And as long as a tank doesn’t leak, you certainly can buy used equipment. I checked online, and a plain 10-gallon glass aquarium from Walmart is $15. So, no one can say this is a ridiculously expensive purchase, although you will need some kind of simple filter to run on it, and maybe an air stone. And a place to put it.

There is one teeny tiny bit of bad news here. You shouldn’t put a Qtank or Htank within 10 feet of your display tank or within 10 feet of any other Qtank or Htank or any tank. Sorry. Why? Because we already know that Marine Velvet (Amyloodinium occelatum) can be transmitted through the air in aerosolized droplets. We also know that freshwater ich (Ichthyophthirius multifiliis) can be transmitted that way too. So, it’s also likely that marine ich (Cryptocaryon irritans) can also be transmitted like that. The good news is that you can get away with small tanks for your Q and H tanks unless you’re planning on raising Hammerhead sharks.

If you are devoted to this hobby, sooner or later, you will need two of something that you can use for medical treatment and/or quarantine. Just don’t wait until an emergency. Some people keep a Qtank up and running all the time. At least keep enough saltwater, mixed and aged, that you have available if you need it. We’ll cover Q and H tanks in more detail in a future article.

3. Sterilization: You probably already know that we can’t use any cleaning products or soap to wash aquariums or aquarium tools. But there are things that we can use. Bleach is one and Potassium Permanganate is another.

If you’re using bleach, and the bleach is 5.25% sodium hypochlorite (mine isn’t labeled, so I emailed Clorox) then 10 ml in 0.5 liters of water will “disinfect” or sterilize whatever. That’s 20 ml bleach in one (1) liter of water. There are different strengths of sodium hypochlorite, so you would need to know what you have.

So, if you want to sterilize an aquarium, rinse with tap water, then fill with an appropriately measured bleach solution, let it sit for 15 minutes, then pour it out. Rinse well with RO/DI water again and allow to dry by air. Sometimes things that have been sterilized in bleach have a lingering “bleach-y” smell, but that’s not a problem. The smell does go away. In Europe, baby bottles are commonly sterilized with bleach.

This same solution of bleach and water can sterilize nets, instruments, tweezers, knives, or whatever you use regularly. Use RO/DI water for the final rinse.

If you don’t want to use bleach, you can also use potassium permanganate. Potassium permanganate is an inorganic compound and strong oxidizer. It has many industrial and medical uses, and is in fact on the WHO Model List of Essential Medicines. It comes in a jar and it’s a crystalline substance.

Potassium permanganate is not hard to get either. I looked briefly online and even found it on Amazon. I live in Canada, and I usually order it through my pharmacy.

But wait a minute. Potassium permanganate (KMnO4) is strong stuff. It can start a fire if it’s in contact with the wrong substance. You need to be very careful working with it. I’m talking about eye protection, gloves, and a mask. You don’t want to get it on you; you don’t want to breathe it, and you definitely don’t want to get any in your eyes. I mean the same is true of bleach, but KMnO4 is powerful stuff. Don’t use it unless you’re prepared to be VERY CAREFUL. This stuff will shred your skin and melt your bones.

If you do want to use potassium permanganate, then you will also need to have some (hydrogen) peroxide on hand to neutralize it. I buy peroxide by the case at Costco. All you do is rinse whatever needs sterilizing with plain tap water (instruments or basin or empty aquarium), fill the basin or aquarium with tap water, place instruments inside (if needed), then add a little potassium permanganate, like a half of a teaspoon at a time until the water turns a bright pink/fuchsia color.

When you get that color, just let it sit for 15 minutes. Then add peroxide to neutralize it. Add enough peroxide to make the solution clear. When it’s clear again, you can discard the solution and everything is sterile. Rinse with RO/DI water and Bob’s your uncle.

Store chemicals in a safe place out of the reach of children and pets. Store potassium permanganate in a cool, dark place.

Potassium permanganate, by the way, is being studied for treating both freshwater and saltwater fish as a four-hour bath in a solution of 2 mg per liter of water because so many fish diseases start as external diseases. But we are NOT suggesting that you start experimenting with it on your marine fish, and some fish are more sensitive to it than others. This is not mainstream usage among hobbyists (yet), and it does seem to be more popular among freshwater enthusiasts than reefers. It is, however, good for sterilization, so it’s worth mentioning.

I’m sure you already know that you should not be sharing the same tools between a DT, QT, and HT unless you’re sterilizing them first. Either sterilize or have separate sets of tools for each tank. But sterilize anyway. Sorry.

It would be a good idea to have some of these things I’ve mentioned on hand for when you need them. Some aquarists never purchase in advance. The problem here is that when you need it, you tend to need it RIGHT NOW. You will have difficulty buying supplies on Christmas weekend when you have a sick fish. Take the time and trouble to have a proper quarantine tank set up and use it with clean instruments for anything that is going into your display tank. Anything.

In Part 2, we’ll talk about fish medicine.


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About the Author: Cynthia White


Cynthia received her BA in English from NYU during the Paleozoic Era. She has been a freelance writer and editor for over 20 years. She has written for newspapers and magazines, both in print and online, and writes ebooks, press releases, and sales and marketing copy. She was formerly a Marketing Manager for a small oil company. Her portfolio can be found here. Now she is a writer and editor on staff at R2R, where her forum nickname is Seawitch. Her build thread can be found here.

For 15 years, she kept a dozen freshwater tanks, bred cichlids--Cyphotilapia frontosa--and sold them to pet stores in Calgary. Finally, after years of study, she has come to saltwater side. She lives in British Columbia, Canada, with her husband and three special-needs dogs, a five-minute walk from the Georgia Strait.