aqua_chem
Aquarium Advice Addict
A though occurred to me the other day on this topic.
In regards to pathogens: Do we shelter out fish? The more I think about it, the more I have to say yes. However, I feel that we are obligated to due to evolutionary circumstances.
Disease immunity has two major qualities: evolutionary and acquired. The later has already been discussed, but the other has been largely neglected. One only has to look at the case of sub-Saharan African populations and African trypanosomiasis, or "Sleeping Sickness," to see what I'm talking about. This disease is endemic to this area, and results in many casualties each year. Because of this, the populations of the area have adapted to increase the survival rates against this disease. One of the most well known adaptations is the prevelance of sickle cell anemia, which is found very commonly in this area. Both the carriers and the affected carry a resistance to the disease, and thus the gene is selected for. Imagine, if you will, that african trypanosomiasis established itself in the US. Many people would die, as they do not have evolutionary adaptations against the disease.
Now, take a look at your fish tank. More than likely, you will see fish from many different areas: central america, S. America, eastern and central Asia. Now imagine that these fish all brought in their native pathogens. Not a pretty site. This is why we must strive for sanitation in our tank: our fish have not even evolved to take on more lethal strains, much less the natural immunity.
As far as water quality goes, the exact quality of water varies widely around the world. Some water is cleaner, other is dirty. But if you once again look at the problem from an evolutionary standpoint, some fish have adapted for pristine water, or rather haven't adapted for nastier water, whereas other have. I think some common sunfish (bluegil I think) have an ammonia LC50 of near 100 ppm! However, when we bring these fish together in a tank, it is almost 100% sure that the water tolerance of all the fish is not the same. This is why we must maintain the quality: too clean water has never (that I'm aware of...) kill a fish, but you can't say the opposite is true.
In regards to pathogens: Do we shelter out fish? The more I think about it, the more I have to say yes. However, I feel that we are obligated to due to evolutionary circumstances.
Disease immunity has two major qualities: evolutionary and acquired. The later has already been discussed, but the other has been largely neglected. One only has to look at the case of sub-Saharan African populations and African trypanosomiasis, or "Sleeping Sickness," to see what I'm talking about. This disease is endemic to this area, and results in many casualties each year. Because of this, the populations of the area have adapted to increase the survival rates against this disease. One of the most well known adaptations is the prevelance of sickle cell anemia, which is found very commonly in this area. Both the carriers and the affected carry a resistance to the disease, and thus the gene is selected for. Imagine, if you will, that african trypanosomiasis established itself in the US. Many people would die, as they do not have evolutionary adaptations against the disease.
Now, take a look at your fish tank. More than likely, you will see fish from many different areas: central america, S. America, eastern and central Asia. Now imagine that these fish all brought in their native pathogens. Not a pretty site. This is why we must strive for sanitation in our tank: our fish have not even evolved to take on more lethal strains, much less the natural immunity.
As far as water quality goes, the exact quality of water varies widely around the world. Some water is cleaner, other is dirty. But if you once again look at the problem from an evolutionary standpoint, some fish have adapted for pristine water, or rather haven't adapted for nastier water, whereas other have. I think some common sunfish (bluegil I think) have an ammonia LC50 of near 100 ppm! However, when we bring these fish together in a tank, it is almost 100% sure that the water tolerance of all the fish is not the same. This is why we must maintain the quality: too clean water has never (that I'm aware of...) kill a fish, but you can't say the opposite is true.