Originally Posted by
IbanEz
http:///forum/post/3241914
True to some extent, although only for aesthetic reasons IMO, because if you are not worried about aesthetics, You could in fact have a system that is mostly self contained with the right choice of fish and the right size and aquascape. For instance, You could have a 90 gallon tank with live rock, rubble, deep sand bed, and macro algae, a pair of mandarins and the introduction of pods, and would only require top offs, theoretically.
In the ocean, the nitrogen cycle certainly is a cycle. The ammonia turns to nitrite, nitrate, and nitrogen which in turn feeds alga and plants. When these things are eaten by fish and other organisms, they produce ammonia and we have a cycle.
In most cases, this can't be (or isn't) replicated to a T in our tanks. I don't think it's worth rewriting the books for.