Over-dosing is better than Under-dosing. Treating your fish effectively and safely

Over-dosing is better than Under-dosing. Treating your fish effectively and safely

Written by George J. Reclos Wednesday, 19 May 1999 01:00

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Over Dosing is better than Under Dosing but No Dosing is the best !

At one point or another, disease is going to appear and perhaps even spread in your tank. It may start by infecting  just one fish or as an epidemic situation where more fish have the same disease. Then you open your books (I assume you have at least one book on fish diseases), ask your local pet shop guy (who sells you tons of "high-tech" medications) or E-mail the disease guru you know to seek advice. The answer will most probably be the same, and it usually reads like that : "Your fish has probably got the x disease which means you should isolate it and treat it with the z medication". So far so good. At least you have an answer and the next step is to follow the guru's suggestion : isolate the fish and treat it with a suitable medication.

Firstly, in some cases, the reasoning for isolating the fish is questionable. If the fish is heavily infected with external micro organisms then, most probably, other fishes are infected too, or the micro organism is present in the water column. It is common sense that the micro organism was present in the water and this is how the fish was infected--so probably it is still in the water, too. An exception is when the infected fish is a new addition which was not quarantined - the only difference being that the micro organism was not present before the infection but was introduced by you. It sounds reasonable to assume that, in  this case, treating the whole of the tank is preferable (unless you have as many hospital tanks as fishes). I will use the term "micro organisms" in the broad sense i.e. it shall include fungi, bacteria, protozoa and viruses.

To start with, there is nothing you can do for viral infections. Viruses are a special king of micro organism which, simply put, is at the borderline of life. These very tiny micro organisms have the ability to transform and adapt easily and even "die" if they need to. Of course, they do not die. What they do is they transform in a new stage which is very resistant while there are no signs of life as we know it. They do not breath, they don't metabolise, move or reproduce at this stage. Needless to say, there is simply no medication that works (not even for humans, with notable exceptions). When you deal with a viral infection you have to rely on the good condition of the immune system of your fish. That is another good reason to keep them in prime shape and this is why stressed fish is always prone to viral infections. In this case, you may see you fish being lazy, refraining from eating or lying on the bottom for a couple of days and then behave normally again. Now we have covered the exception. Needless to say, for us, the hobbyists, there is no way to discriminate between a viral infection and an internal bacterial infection so the point I made was mostly academic. Only a post-mortem section, performed by a specialist might reveal the true cause of death. If you have a tank full of really expensive species perhaps this is what you should do. Bear in mind that viral infections will usually spread, so you have to take advantage of the time it will take the virus to reproduce. Of course, all you can do is isolate your fishes (one in each tank) and hope that you were quick enough. What we normally do is take note of the signs, guess what the disease is (the serious keeper may even read a couple of books, surf the net or seek professional advice) and use the right medication at once. Of course, the "right" medication may not be right at all, but you don't know it, do you? On top of that, if the situation looks hopeless, doing something is better than doing nothing, which is exactly the theory most of us usually follow.

We now assume that we use a given medication and we have correctly identified the infection to be a bacterial (or fungal or protozoan) one. Firstly, we should read what the package insert says. There is a reason they put these leaflets in the boxes you know. The reason is for us to read them. And they want us to read them because they include some very useful information on that piece of paper. So take the time to read it carefully. Take all the precautions / preparatory steps suggested. Make sure this medication is meant to treat the disease you are trying to treat. If you note sentences including "may treat some cases of" or "occasionally potent" followed by the disease's name, forget it. Always keep in mind that the narrower the spectrum of a medication the more potent it usually is. All around players usually give you an average efficacy all around. When preparing disinfectants (meant to treat surfaces or tools) companies may include very potent active ingredients that will kill any pathogen within seconds. Since these ingredients will also kill a fish (or even a human) within seconds they can't be used in medications. So, when a preparation is to be used on living organisms it must contain substances that can act on the pathogen while not harming the hosting organism. This, of course calls for more specialized products, which need some conditions in order to act the way they should. The reason for this is that the medication must be present in concentrations within the therapeutic range.

What is that? If we assume that the pathogen is killed at concentration x while the fish is killed at concentration 5x then the therapeutic range of this medication is between x and 5x. Very clear and I am sure it makes sense. The key point here is that the medication's concentration must be over x and definitely below 5x. The precautions stated in the insert give you the conditions under which what you add in your tank is what will work. This assumes that you have already created the right conditions for this medication. Thus you should immediately remove activated carbon if it says so. Increase aeration if so advised (increase it anyway I would say, unless otherwise stated). Raise the temperature if needed. Do not add chlorine removers if so stated. Better still, perform a large water change before adding the medication (in order to remove as much of the conditioner as possible). Pay special attention to the "small letters". In some medications you have to remove ammonia removers, or salt. Some medications may affect your water parameters so you may need to compensate for that. I was nastily surprised when I used a "peroxide releasing" product, which lowered the pH of my tank from 8,4 to 7,0 in an hour. Turn off the lights of your tank for the whole course of the treatment if the medication is light sensitive (example : tetracycline). If direct or indirect sunlight reaches your tank, cover it with a towel or blanket. Follow these rules. If you don't you are simply under-dosing. Under dosing means that the actual concentration of the medication in your water is lower than the minimum lethal concentration recommended for that particular micro organism or, the duration of exposure is shorter than the minimum lethal exposure. In both cases you have - or you may have - a very serious problem. The same is true when you calculate the volume of your tank. Instead of guestimating how many litres your rocks occupy, take my advice : ignore the rocks. Treat the tank as if it was full of water. This is over-dosing. I am sure that you can reverse the definition for under-dose.