Is a RODI top off considered a water change?

I never did water changes in my old 180 tank because I had such tremendous evaporation I was getting a few gallons a day of new RODI water introduced to the system to compensate for evaporation.

For years my LFS said I should be doing bi weekly water changes and I could never understand if the water change was supposed to replace the salt or the water.

Is a water change more about switching the salt? If its about switching the water I would think the RODI was performing that function.

 

Your avatar scares me

No, topping off is not considered a water change. Water changes are performed to dilute pollutants in the water and to replenish trace elements that have been used by the tank inhabitants.

 

So its about the salt? not the water?

 

Sorry, looks like you posted while I was editing my post. It's a little of both

 

I think I just found the answer.
It is all about diluting the gunk that mechanical and biological filtration simply can not remove.
By removing 10 percent of the water, you are removing 10 percent of the gunk. Then adding fresh mixed salt water dilutes the remaining 90 percent of the gunk.

 

Correct but trace elements also need to be replaced and water changes with a good salt mix will do that as well.

 

What about API's trace element additive. I do 10 % water changes about every 10 days or so and also add the trace element... am I over doing it?

 

I have no idea what that product contains nor what you have in your tank that may be using those elements so I can't answer the question. Also, if you're adding trace elements and not testing those levels, you could be headed for a fall.

 

If you put a clean pair of underwear on over your dirty pair would you consider that an underwear change? Get my point

 

What if you prefer going commando?