No Water Change's

[dkeller_nc]

If you don't, you're dosing without measuring at every water change. Synthetic sea salt composition between all the makers can vary greatly between batches.

This isn't quite the same thing, though you do have a point about variations in minor/trace elements between different batches of sea salt. If you're dosing trace element supplements but doing no water changes, then this equation applies (basic chemical engineering mass balance, FWIW):

Accumulation = In - Out + Generation

Since in the case of trace elements, generation = 0, then whether accumulation has a positive or a negative sign depends on the rate that the life in the tank is sequestering a particular trace element (that's the "out" term) and how much one is dosing (that's the "in" term). More than likely, the "accumulation" term is going to be positive by a large order of magnitude if one is dosing and not doing water changes to remove excesses.

Note that the above situation is not the same thing as replacing trace elements with water changes. In this case, it will never be possible to exceed the concentration of the particular ion in the salt mix, and depending on the rate and amount of water changes, the amount of a trace element is very likely never to go close to zero, either. Note that this only applies to trace elements that are co-factors for enzymes and are used in extremely small quatities, not to minor elements that are used in skeleton building, such as strontium.

 

[FlyPenFly]

I agree that water changes will always keep not in demand elements at a level set by the salt maker. You will be in a position where you may not be adding enough of something that is being used up. That is however much safer than continually adding in something that might accumulate.

Personally, I do dosing + water changes.