Originally Posted by Aquarius Keeper
Well, I understand about ammonia and nitrite, but I still don't understand why FW aquariums can tolerate 10-40 ppm nitrate bit saltwater tanks can't tolerate any??
Mind you I'm not trying to keep corals here...
SOME freshwater fish are very Nitrate tolerant. Some are not. Anyone who has kept Danios understands that Nitrates of 100 ppm are not going to phase this fish. On the other hand, Nitrates of 20 ppm would be cause for alarm in an aquarium with a Uaru, Discus, or other sensitive species. Some fish are more tolerant of captivity than others. That is just the way it is.
Saltwater fish are used to an environment that is much more stable than freshwater. The water chemistry in the ocean changes very little over time, maintaining constant levels that must be maintained in order to be successful in the aquarium.
Another factor is way fish interact with water. Freshwater fish absorb water thru their skin. They don't actually drink. Saltwater fish directly drink the water. This is a huge distinction that makes the 2 systems 100% different when it comes to the required water parameters.
The simple fact is that saltwater has a different makeup of salts and major ions than freshwater, causing the fish to have evolved differently. They behave differently in an aquarium, have different needs, and require different levels of care.
So, the simple answer to your question....