A gorgeous 250G tank

Photo is from the Reef2Reef archives

As I mentioned in Part 1, 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 don’t know what ailment you’re dealing with, then by all means, ask questions there. And you will find several very helpful stickies.

There are aquarists who don’t keep any medicines on hand. Some won’t medicate their fish for philosophical reasons. Others remind us that medicines have expiration dates. There are no aquarium police, and you have to decide what is best for you and your aquariums. I’m not going to debate philosophy, and yes, medicines on your shelf don’t last forever.

This article is for those who want to know what they could have on hand if they should need it and those who want to know the potential benefits they can have from modern fish medicine and chemistry. I’m going to list the medicines that could be useful and list them in the general order of importance—in my mind anyway—but I will try to be as methodical as possible. There’s an old saying that if you ask 10 reef aquarists for an opinion on a given topic, you will receive 12 answers. I’m pretty sure this applies here as well. The order you place these medicines may be different. The information I present, however, is well documented.

Before I continue, there’s one point I’d like to make. In the US, the Occupational Health and Safety Administration has a Hazard Communication Standard (HCS or HazCom) program, and in Canada, the closest equivalent is the Workplace Hazardous Materials Information System (WHMIS). A couple of rules in these programs apply to reefers:

A. If you mix your own medicines, stock solutions, chemicals, lotions or potions, ALWAYS label what you have mixed unless you’re going to finish all of it in one go. If you don’t have fancy labels, then use duct tape. Use anything. And NEVER decant a chemical or medicine from one bottle to another UNLESS you label it carefully.

B. NEVER taste something if you don’t remember what it is. (This may sound stupid, but I’m not being flip. Accidents happen and people die. What if you used some pretty bottle you were saving for some stock solution that you don’t remember?)

Assorted Glass Bottles

Photo is a royalty-free image from Pexels

C. Always label any special tubs or buckets or containers if you use them for your aquarium. If you’re unlucky enough to have your roommate use your saltwater bucket for Mr. Clean to wash your floor, then you’re going to have a sad day ahead.

D. Put the number for Poison Control on your fridge. However, if you live in a big city, the 9-1-1 dispatcher can probably patch you in to Poison Control. Most chemical or pharmaceutical companies have a number you can call for information, but if it’s an emergency, like you breathed in something and feel unwell, call 9-1-1 in the US or Canada. Or as the proverb goes, "He who hesitates is lost."

Many of these medicines below are large topics in and of themselves. I will examine some of them in more detail in future articles.

1. Copper: I’d put this at the top of the list because it can be used to treat several different ailments including Marine Ich and Marine Velvet, Cryptocaryon irritans and Amyloodinium ocellatum respectively. What’s important to understand about copper medicine is that the therapeutic window is small. So, if you give too much, you kill your fish; if you give too little the medicine doesn’t work. This means that you have to test carefully and continuously so you know how much of your copper medicine is in the water. The second issue is that there are several different copper compounds sold by different companies, and different test kits are more or less accurate with the different copper compounds. So, you have to have the right test to match the compound you use. Copper is also lethal to invertebrates so you can never never ever dose your display tank, or bye bye everything except the fish, assuming you dosed correctly.

I found a good detailed article about copper medicine here. And there is also detailed information in Humblefish’s thread that I mentioned earlier. And here is some great information from the University of Florida.

Copper, symbol Cu, is a heavy metal that has been used to treat both marine and freshwater fish for many years and has been used by man for a variety of purposes for thousands of years. You can buy copper medication at your local pet store selling fish products (LFS) or online.

Copper Wire

Photo is a royalty-free image from Pixabay

2. Methylene Blue: Methylene Blue is next for me. It’s actually methylthioninium chloride, and it’s a drug on the World Health Organization List of Essential Medicines. Yup, humans take it, too. For marine fish, at low doses, it converts methaemoglobin to haemoglobin. In other words, at low doses it calms fish and helps their oxygen uptake. It’s usually used as a part of a freshwater dip or bath for a newly arrived fish and can help combat cyanide poisoning, which we know is one way that wild fish are captured. It’s effective at ridding a fish of some external fungi and some external parasites. It will stain anything and everything blue. I have seen references to using two (2) drops per liter of water, but since different brands may have different strengths, read the label and follow the instructions. Bob Fenner, the famous marine aquarist, breeder, and author is a big fan of it, and that’s good enough for me. You can buy methylene blue at your LFS or online.

3. Oil of Cloves: Remember the movie, Marathon Man? Clove oil is best known for relieving tooth or gum pain, although the FDA in the US has not approved it for this purpose. Clove Oil has several ingredients, but what it has the most of, and what interests reefers the most is eugenol. Eugenol is used for sedating, anesthetizing, or euthanizing fish.


Photo is a royalty-free image from Pixabay

Now, I don’t know why a home aquarist would need to sedate a fish, but it can also be used for euthanasia. Fish euthanasia is a big topic, which I would prefer to address in its own article. So, suffice it to say that if you want one drug on hand to handle this in an emergency, eugenol or clove oil is the easiest one to get.

Jennifer Buchanan, a Project Biologist for InStream Fisheries Research, told me that they use clove oil in the field to mildly sedate fish for very short periods for safe handling. Eugenol is not soluble in water, so they make a 10% stock solution of concentrated clove oil with ethanol. So, for example, 10 ml clove oil added to 90 ml of ethanol for a total volume of 100 ml is a 10% solution (per unit volume). She said that one (1) ml (about 20 drops) of this solution in one (1) liter of water is enough to sedate a fish. Then when the fish go back into regular water they come out of it instantly and swim away.

Of course, we don’t know what size fish she’s talking about, she probably has pure ethanol to work with, and we don’t know the percent of eugenol in her concentrated clove oil, so it’s impossible at this time for me to tell you exactly how much you would need. This is clearly not an exact science, but if you’re desperate, you have a little information to work with.

Furthermore, Jennifer works mainly with freshwater fish, and we concern ourselves with saltwater fish. However, I found references to using eugenol for sedating, anesthetizing, and euthanizing saltwater fish as well in a University of Louisiana at Lafayette research paper, the American Veterinary Medical Association (AVMA), and the Royal Society for the Prevention of Cruelty to Animals (RSPCA) in Australia. That's some light reading for you in the evening.

Let me stop and say a word about ethanol, which is the alcohol people drink. Unless you’re a scientist, you probably can’t get pure ethanol. But we can probably get vodka (about 40% alcohol), or Everclear (about 75% alcohol). I won’t mention Moonshine (up to 90% ethanol) because Reef2Reef does not condone illegal activities.

I live in a small town in British Columbia, Canada. I can buy Everclear at a local liquor store, although it is not visible on the shelf, and the manager decides if he’ll sell it to a customer on a case-by-case basis. (He said he’d sell it to me.) Up here, Everclear costs $42.99CAD for 750 ml. In US dollars, that’s about $32.67 as of this writing. Not cheap, but maybe they have smaller sizes. In the US (Kansas), Everclear is 95% alcohol and costs US$17.99 for 750 ml. Hmmmmmm.

So, for euthanasia with eugenol, in an emergency, it’s possible to sedate the fish first with a stock solution, then once the fish is obviously sedated, just add more alcohol. Alcohol alone would make the fish suffer, which we obviously don’t want.

If you’re buying clove oil, try to buy clove oil for which the eugenol content/percent is labeled. Oil made from the stems has the highest proportion of eugenol. You can buy it online or in a natural food store.

There are more medications that I want to list here, but I think this is enough for Part 2. Tune in next week for Part 3 when we’ll examine the exciting topic of anti-fungal, anti-bacterial, and anti-parasitic meds for your Reef Medicine Cabinet.

NB: In my previous article, Part 1, I mentioned that I wasn’t sure how much sodium hypochlorite was in the bleach that I buy. I thought it was 5.25%. I wrote to Clorox, and they kindly replied, saying that it was, in fact, 6% sodium hypochlorite. Bonus. See below.


Photo is courtesy of Cynthia White, 2018
Screenshot of conversation with Clorox
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Photo/Screenshot courtesy of Cynthia White, 2018

Special thanks today are due to Jennifer Buchanan, who is happy to answer my relentless questions; and Reef2Reef forum user, hdsoftail1065, who kindly did some research for me in Kansas.

We encourage all of our readers to join the Reef2Reef forum. It’s easy to register, free, and reefkeeping is much easier and more fun in a community of fellow aquarists. We pride ourselves on a warm and family-friendly forum where everyone is welcome. You will also find lots of contests and giveaways from our sponsors.


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, as well as written ebooks, press releases, and sales and marketing copy. 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.