I must seem like a broken record on this forum sometimes always diagnosing what is, in my opinion, one bacterial infection after another. And to some, it must seem like "the easy way out" to explain away many ailments as just another bacterial infection. But below are my reasonings for why I believe bacterial infections are so rampant in this hobby:
We all know the water in our aquariums are full of bacterium. Most of it good (like nitrifying bacteria), but some of it can be bad (like the kind that causes bacterial infections in fish). The bad kind is usually kept at bay by a healthy fish's natural immune system. Or if the fish becomes "sick" and actually displays symptoms of a bacterial infection; many times the immune system is able to fight it off without the aid of antibiotic medication. So if you stop and think about it, these bacterial infections in fish are akin to humans and our never ending battle with germs, viruses, and of course, infections.
Many factors can make a fish more susceptible to infection. Of course, a cut or open wound being the most obvious. Poor water quality can also be a factor. But anything that lowers the fish's overall immune system can make infection more likely. Stress (i.e. fish fighting), malnourishment, or if the fish is battling an ongoing parasitic infection (i.e. Ich) makes a "secondary" bacterial infection possible. For example, back when I practiced "Ich management" it seemed periodically I always had a fish with popeye, or some suspicious red mark or similar. But now that I QT and prophylactically treat all my fish, I almost never see anything that might be an infection on any of my fish.
Gram positive vs. gram negative: The majority of bacterial infections seen in established fish are caused by gram positive bacteria. This is especially true if no new fish have been added to the aquarium in a while. Gram positive bacterial infections are the kind most fish can deal with successfully on their own (symptoms may be barely noticeable). Now, gram negative bacterial infections are most often seen in newly acquired fish, and are more likely to require antibiotic treatment. In fact, some fish can die within 24-48 hrs of showing symptoms due to the aggressive nature of some gram negative bacterium. These strains can easily overwhelm the fish's natural immune system. Unfortunately, there's no easy way of visibly differentiating gram positive from gram negative bacterial infections (without taking a sample and then using a staining process). The saying, "if it looks really bad or is widespread" denotes a gram negative infection is oftentimes true, but not 100% of the time.
So, what does a bacterial infection look like? Sometimes it's self-describing: Popeye/cloudy eyes, fin & tail rot, dropsy (bloated fish), etc. But some other bacterial infections, such as furunculosis, hemorrhagic septicemia, etc., can have varying visible symptoms. Any "redness" or open sores/wounds on a fish should be viewed with suspicion. Also, a white film or "fungus" looking growth can denote a bacterial infection. However, these visible symptoms can also mean something entirely different. For example, redness around the gills is a symptom of ammonia burn, and a white "cauliflower-like" growth on the fins & spines is most likely just Lymphocystis; a harmless virus found in many fish. So, doing proper research and not just lumping everything into one category is vital. Whether or not a bacterial infection is contagious is highly dependent upon the strain you are dealing with, and the conditioning of your other fish. So, no easy answer.
How to treat a bacterial infection: First off, there are many things you can do to prevent a bacterial infection from happening in the first place. Maintaining proper environmental conditions (i.e. clean water) for your fish to live in being the most vital. Also vital IMO is fish QT; to prevent parasites and other nasties (including harmful gram negative bacterium) from being introduced into your DT in the first place. This will eliminate the possibility of a "secondary" bacterial infection occurring while the fish's immune system is already compromised from battling parasites. It is also my opinion that proper nutrition (i.e. nori, foods high in protein), and periodic use of "fish vitamins" can boost a fish's immune system and help it to cope with possible infections. Some vitamins for fish include the products Selcon, Zoecon and Vita-chem. However, just soaking pellets in Omega-3 fish oil can also help (props to Paul B). I also believe running a UV sterilizer may help in certain situations, as that will lower the overall number of bacterium found in the water.
When to medicate: Sometimes all the vitamins and proper nutrition and clean water is just not enough. Sometimes a fish's natural immune system needs a helping hand (like our own). When to QT and pull the trigger on using antibiotics is not an easy decision. It's a judgement call; whether or not the fish can handle it on it's own. As a general rule, I only pull & treat if: a) The fish looks pretty bad or b) It's a newly acquired fish showing signs of infection. The latter is an easy call for me as all newly acquired fish are in QT anyway. Below is a list of antibiotic medications you can use - it is not a comprehensive list by any means, but just some readily available suggestions. Whatever medication you go with... be sure it contains broad or wide spectrum antibiotic(s) capable of treating both gram-positive and gram-negative bacterial diseases.
We all know the water in our aquariums are full of bacterium. Most of it good (like nitrifying bacteria), but some of it can be bad (like the kind that causes bacterial infections in fish). The bad kind is usually kept at bay by a healthy fish's natural immune system. Or if the fish becomes "sick" and actually displays symptoms of a bacterial infection; many times the immune system is able to fight it off without the aid of antibiotic medication. So if you stop and think about it, these bacterial infections in fish are akin to humans and our never ending battle with germs, viruses, and of course, infections.
Many factors can make a fish more susceptible to infection. Of course, a cut or open wound being the most obvious. Poor water quality can also be a factor. But anything that lowers the fish's overall immune system can make infection more likely. Stress (i.e. fish fighting), malnourishment, or if the fish is battling an ongoing parasitic infection (i.e. Ich) makes a "secondary" bacterial infection possible. For example, back when I practiced "Ich management" it seemed periodically I always had a fish with popeye, or some suspicious red mark or similar. But now that I QT and prophylactically treat all my fish, I almost never see anything that might be an infection on any of my fish.
Gram positive vs. gram negative: The majority of bacterial infections seen in established fish are caused by gram positive bacteria. This is especially true if no new fish have been added to the aquarium in a while. Gram positive bacterial infections are the kind most fish can deal with successfully on their own (symptoms may be barely noticeable). Now, gram negative bacterial infections are most often seen in newly acquired fish, and are more likely to require antibiotic treatment. In fact, some fish can die within 24-48 hrs of showing symptoms due to the aggressive nature of some gram negative bacterium. These strains can easily overwhelm the fish's natural immune system. Unfortunately, there's no easy way of visibly differentiating gram positive from gram negative bacterial infections (without taking a sample and then using a staining process). The saying, "if it looks really bad or is widespread" denotes a gram negative infection is oftentimes true, but not 100% of the time.
So, what does a bacterial infection look like? Sometimes it's self-describing: Popeye/cloudy eyes, fin & tail rot, dropsy (bloated fish), etc. But some other bacterial infections, such as furunculosis, hemorrhagic septicemia, etc., can have varying visible symptoms. Any "redness" or open sores/wounds on a fish should be viewed with suspicion. Also, a white film or "fungus" looking growth can denote a bacterial infection. However, these visible symptoms can also mean something entirely different. For example, redness around the gills is a symptom of ammonia burn, and a white "cauliflower-like" growth on the fins & spines is most likely just Lymphocystis; a harmless virus found in many fish. So, doing proper research and not just lumping everything into one category is vital. Whether or not a bacterial infection is contagious is highly dependent upon the strain you are dealing with, and the conditioning of your other fish. So, no easy answer.
How to treat a bacterial infection: First off, there are many things you can do to prevent a bacterial infection from happening in the first place. Maintaining proper environmental conditions (i.e. clean water) for your fish to live in being the most vital. Also vital IMO is fish QT; to prevent parasites and other nasties (including harmful gram negative bacterium) from being introduced into your DT in the first place. This will eliminate the possibility of a "secondary" bacterial infection occurring while the fish's immune system is already compromised from battling parasites. It is also my opinion that proper nutrition (i.e. nori, foods high in protein), and periodic use of "fish vitamins" can boost a fish's immune system and help it to cope with possible infections. Some vitamins for fish include the products Selcon, Zoecon and Vita-chem. However, just soaking pellets in Omega-3 fish oil can also help (props to Paul B). I also believe running a UV sterilizer may help in certain situations, as that will lower the overall number of bacterium found in the water.
When to medicate: Sometimes all the vitamins and proper nutrition and clean water is just not enough. Sometimes a fish's natural immune system needs a helping hand (like our own). When to QT and pull the trigger on using antibiotics is not an easy decision. It's a judgement call; whether or not the fish can handle it on it's own. As a general rule, I only pull & treat if: a) The fish looks pretty bad or b) It's a newly acquired fish showing signs of infection. The latter is an easy call for me as all newly acquired fish are in QT anyway. Below is a list of antibiotic medications you can use - it is not a comprehensive list by any means, but just some readily available suggestions. Whatever medication you go with... be sure it contains broad or wide spectrum antibiotic(s) capable of treating both gram-positive and gram-negative bacterial diseases.
- Erythromycin & Minocycline combination (This "combo" is basically the same as Maracyn 1 & 2. The s/w version has been phased out, but you can use f/w Maracyn 1 & 2 so long as you double the dosage for s/w use (which can get expensive). The alternative is to buy something like API E.M. Erythromycin, and then order Minocycline off the Internet. I advocate using this combo above all others because in 35 years of fish keeping I have found it to be both effective and have minimal side effects. The only downside is it can be slow acting.)
- Furan-2 (Good for aggressive infections when help is needed ASAP. Downside is it can pretty harsh on certain fish.)
- Kanamycin aka Seachem Kanaplex (I have very limited experience using this product - as in, only once.
But I was very impressed with it, and the tank full of fish I used it on are recovering nicely.)
- Nitrofuracin Green Powder (No actual experience, but I have read very good reviews on this product. Supposedly it is also useful for healing wounds and treating ammonia burn.)
- Maracyn Plus (No actual experience, and I have read not so good reviews. This is Mardel's "replacement" for s/w Maracyn 1 & 2. :furious
