Originally Posted by jeffaquarius
You might be referring to mag, cal, strontom, iodine and etc. Yes corals need them but not fish.
Nope, not at all what I meant.
Here is an excerpt from what I read.
Water Changes in the Aquarium
"Water changes do two things simultaneously. Most importantly they remove all the bad things that build up in the aquarium over time. These things include nitrate, phosphate, growth inhibiting hormones that many if not most fish give off, dissolved organic compounds, and other things. Although nitrate is far from the only bad thing that builds up, or even the worse, in unplanted tanks it does correlate very well with all of the other things that build up. This is why so many people make such a big issue out of nitrate. The other things are at least as important, we just don't have test kits for them (except phosphate). The other major function of water changes is to bring in good things that are used up over time. The end result of all the biological activity in an aquarium is acidification. This uses up the KH
in the water. As the KH
isused up the pH wil decrease. Eventually the pH can crash. There are many other vital minerals and trace elements needed that are replenished with water changes.
Water changes also have a massive impact on stocking. It is an error to discuss stocking without addressing water changes and water quality. Discussing stocking based on tank size alone is not different then simply going by one of the very errored 'one inch per gallon' type guides. Experiments have shown that it is the water quality, not tank volume, that stunts fish. Discus were raised in two different setups. One was a twenty gallon tank that was heavily stocked and received very large daily water changes. The other setup was a fifty five gallon tank with a small fraction of the number of fish and did not receive any water changes. The discus in the twenty gallon grew at a normal rate while those grown in the fifty five were severely stunted. The experiences of many other aquarists support the results of this experiment, demonstrating that it is definitely water quality, not volume, that is the active factor in stunting fish. Obviously there is still a minimum tank size for fish based on size and activity leve. Please see the Stocking an Aquarium article for more information. The volume of the tank has a minimal impact on water quality."