My theory is that an uncycled tank with small fish can be handled with standard carbon filtration for the most part. That said, there must be something to all this written material about the nitrogen cycle (there are too many smart people in the hobby to be wrong). I think it probably pays off in the long run and especially for situations with larger fish or larger bio-load situations.
In addition to the fact that carbon does not stay active for more than few days in most cases, Carbon does nothing whatsover for ammonia.
Ammonia cause permanent gill damage and subsequent scarring. nitrite cuases less permanent damage, but weakens fish significantly, opens the door for other complications, and can cause permanent brain and organ damage due to lack of oxygen during exposure.
Many of us kept fish in ignorance, How long did they live? How many times did a fish die prematurely with no Explanation? What was the water parrameters to begin with? Do they compare to water parrameters of modernized municiple treatment plants?
Compare Natural life spans to your experiences, in most cases a properly kept fish will exceed natural life spans in our tanks. In other words if your Oscar died before it was 10 years old, you should investigate a bit. If your Goldfish lived less than thirty, He died prematurely. The really knowledgable fish keepers have the same fish they had years ago for a reason. They never had to replace them.
If you owned a dog and fed it nothing but meat fat and kept it in the garage without cleaning it's entire life it would survive for many years, but no where near as long as it would survive if it had a good diet, exercise, and a clean environment.
Dave
