--
You were questioning the reason to change water
based on nitrates...

I am not questioning anything, I am answering Adam's (the OP) question. See
above in the thread.


You know, there are much more different ions there
beside NO3-...

Yes, I am aware.

Then you are probably aware also, that 80% of their
levels you cannot measure at home acuratelly.

80% of what levels? Can you be more specific? Doesn't how accurate you
need to be depend on the ion you are referring to?


With partial water change you replenish
ions used up by growing animals/plants in your tank.

I add trace elements (Kent Marine Essential Elements) on a monthly basis.

Each element is used up in a different speed, but you dump
all of them on a monthly basis regardless if you need it or not.

How do you replenish your trace elements? Partial water change? When you
do your partial water change you are removing some percentage of water
(15-20%?) and adding artificial sea salt (usually contains trace elements).
How do you know your tank needs it (trace elements)?

That will lead over time to chemical imbalance and your tank
water will be far, far away from the content of natural sea water
compared to the water mixed from the fresh salt mix.

You are FAR MORE likely to cause a chemical imbalance by replacing a
percentage (15-20%?) of your aquarium water with home made sea water than
you are by doing no water change.



You also remove organic byproducts your skimmer left behind.

Such as?

All these which make your water smell and look yellow.
Corals, other invertebrates, fish and plants constantly
release many substances to the water which accumulate
in the closed system like an aquarium.

My skimmer runs 24hrs a day. The organic compounds it doesn't remove on the
first pass will more than likely be removed on the second, third, fourth or
fifth, etc. pass.

You are not able to measure them or detect them in home situation...

Agreed. Therefore, I have NO reason to question my skimmers effectiveness.
I can only go by the health/appearance of my tank mates. They are doing
fine. All is well. My water is not yellow and it does not smell.

Changing water refreshes the water and brings it back
to its original ionic combination...


The only way YOU would "bring it back to its original" condition is if you
changed 100% of your water. Is this what you are doing? If this is what
you are doing you are doing more harm than good.


Would you be fine if your house was perfectly sealed
from the outside air and you just reduce amount of
CO2 and add oxygen on regular basis but would not
exchange air for years?

Another straw man.

How do you think your house would smell ? :-))

I do not have microorganisms that eat and decompose my excrements, my
aquarium inhabitants do.