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Salt in Fresh (Again)

Comments and criticisms concerning freshwater baths for marine fish.

By Scott W. Michael |

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In this column I will be sharing an e-mail message I received in response to my "Salt Q&A" column in Aquarium Fish International magazine. Because I feel this letter is enlightening and touches on a number of important topics, I've decided to include most of the message to benefit readers.

Q. Quarantining saltwater fish is a fine practice when the situation demands it. But I do not care to quarantine a new fish unless it was received with visible signs of disease that require immediate treatment. Most hobbyists will not purchase a fish that looks sick. And if the fish is eating well, has good body shape and coloration and its behavior is normal for that species then there is simply no need.

All fish have parasites (and other organisms/diseases) on or within their bodies at all times, just like every person has some level of virus or infection at all times. As long as a person eats properly, stays fit and avoids undue physiological or mental stress, these afflictions will remain dormant.

The same holds true for fish. Both humans and fish have immune systems. Stress from poor diet, environmental changes and so on (including mental stress and fatigue for humans) can lead to illness because our immune systems work less effectively when there is excessive stress. Rest and medication may be helpful, along with a reduction of stress. This is also when a fish needs to be quarantined. Not when it's healthy and happy.

Mr. Michael was smart to reiterate the fact that freshwater dips are minimally effective. What he failed to mention is the amount of stress the fish undergoes — not just osmotic stress, but also the stress of being captured (again) and placed in unfamiliar surroundings. He also neglected to observe the fact that many, if not most, hobbyists do not have the knowledge to determine length of time in a dip, or even to diagnose diseases.

In my 20-plus years of successfully keeping saltwater fish I have always maintained (after the first few years of learning) that stress is the number-one cause of disease/parasitic outbreaks within a closed/captive environment. We know that there are many different forms of stress. The stress cycle begins upon capture of the fish in the ocean, and it does not end until it is in its final, new home.

Each time the fish is netted/captured, transferred to a new aquarium whether for quarantine or for show, the fish undergoes tremendous stress. A fish goes from pristine waters with its known companions into an aquarium with (comparably) poor water quality, is fed fish foods it's never had and associates with tankmates from other parts of the world that are unfamiliar. Many fish handle stress fairly well, and once in a retailer's aquariums will resume normal behavior and eating patterns. If the fish has a virulent parasite this is where it will show up first.

We all know it's a good idea to either put a deposit or pay in advance for a fish and leave it at the store for several days after its arrival for observation. Many stores will not sell a fish until it has settled in. You may say this is quarantine, but most stores run a centralized system, so it is not. And you only purchase fish that behave and eat properly.

So why quarantine a healthy fish? This practice should be necessary only when it has been determined that the fish's immune system is unable to battle the affliction and needs that helping hand of quarantine. It's my experience that a fish that has been quarantined for several weeks seems fine, but when transferred to its home aquarium quickly becomes ill again, due to the stress of capture, possibly the stress of being introduced to an aquarium with substandard conditions, or something such as aggressive fish or the lack of shelter or territory.

The concept of a freshwater dip, in my opinion, is at best a ridiculous one. Part of the "trick" in applying this method is to leave the fish in long enough to "explode" the few parasites that would be affected by a hyposalinity treatment without leaving the fish in too long. To me, it is simply medieval medicine.

Fish behavior is the best tool for early diagnosis of an impending problem. It is at this point you must ask yourself, "Why is my fish behaving weirdly?" and move on to asking other questions. "Is the behavior limited to one fish, or is it system-wide?" "Is what I am feeding varied enough, or in proper quantity, or missing something important?" "Is there aggression in the aquarium?" By looking at the forest and not just the one tree, you begin to see possible sources of stress. Correct the problem and 90 percent of the time the fish will heal itself. If the cause cannot be determined, and the fish remains ill, then it's time for quarantine and medication — assuming you have enough knowledge to know what you're medicating for and properly administer the drug(s).

In conclusion, I don't think quarantining a new arrival is necessarily a bad thing, but I feel that too much emphasis is placed on it, and that it simply isn't necessary unless a specific situation demands it. And because freshwater dips are minimally effective, why put the fish through the stress? There are alternatives to this barbaric practice. Alternatives that are safer and just as effective, without having to dump drugs into your water.

A. We agree on many things, especially the fact that stress is the aquarist's biggest enemy. But, I would like to address some of your comments on quarantining, which I believe is an extremely important practice for hobbyists to employ.

Like yourself, I've been keeping fish for more than 20 years, and worked in the retail marine fish trade for more than 10. I've dealt with thousands of saltwater fish and hundreds of marine hobbyists in several regions, and I think I have a pretty good feel for the way both the consumer and retailer think and behave.

You mentioned that there are many stores that will allow a fish to settle in before selling it, which gives the hobbyist an opportunity to observe it for a little while to determine if it is healthy. Unfortunately, very few stores quarantine their fish before selling them, and there are few that will refuse to sell a recently acquired specimen. Most shops do not have the space or want to risk of potential loses that may occur in their shop if they engage in such practices. I know this is unfortunate and potentially bad for long-term business, but it's the truth.

As far as hobbyists are concerned, I have found that there are few who will wait to purchase a saltwater fish. If they see a fish they like, they buy it. I must admit to being guilty myself — buying a fish that I really wanted before someone else bought it. It happens all the time.

Even if a shop holds your fish for several days, this isn't adequate time to determine if a fish is healthy or not. As you know, stress can cause long-term suppression of the immune system, and I would submit that one of the most stressful events in a marine fish's life is being in a shipping bag for hours (in some cases many hours or even days). I have found that most fish usually start to display symptoms of parasitic infection three to seven days after being shipped. These specimens often look great, feed well and display no aberrant behavior indicative of infection. If a customer were to purchase one of these fish a couple of days after it arrived, it could very likely become quite sick after it was transferred to their display aquarium.

And then what? One has to try and extract it from an aquarium that should be full of hiding places, causing more stress for the fish. Not only do we cause stress to the fish now displaying signs of parasitic infection, we presumably will cause some stress to the other inhabitants of the aquarium when we displace the aquarium decor in an attempt to catch the sick specimen.

Also, we may have succeeded in introducing a parasite into the aquarium that was not already present. You're right — fish, like people, are hosts to a number of different parasites and diseases, but not all of these are present on (or in) every fish. For example, in a study conducted on the parasites present on wild and cultured groupers, none of the wild specimens examined were infected by ich (Cryptocaryon irritans) (Leong and Wong 1988). So it is possible that by introducing a fish that was carrying a parasite, like ich, we have exposed our non-infected fish to a new problem!

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Salt in Fresh (Again)

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Reader Comments

Alex    Albany, NY

9/11/2007 4:03:29 PM

Very informative Q & A

Alex    Albany, NY

8/25/2007 10:20:50 PM

Interesting article about fishes..... and humans too. lol.

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