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Threshold
03/06/2015, 10:37 PM
Every once in a while, I've read about people doing a 100% water change.

I come from a fresh water aquarium background (and not much experience with it at that!) so I am not used to more than 30% or so...

Is 100% safe for salt water aquariums because all of the biological filter is there in the live rock and live sand -- so you can replace all of the water without having to cycle the tank?

thegrun
03/06/2015, 10:44 PM
Yes you can make a 100% water change without starting a new cycle, but since there is going to be some major chemical changes it can shock and even kill some livestock. Unless there is some urgent need from say a chemical spill I would avoid any water changes over 30%, and it is best to limit the changes to 15% or at most 20%. Why do you want to make a 100% water change?

Threshold
03/06/2015, 10:46 PM
Why do you want to make a 100% water change?

I am sorry to give the wrong impression. I am just designing my first saltwater aquarium now -- nothing has been purchased or anything.

I had just read about 100% changes and that surprised me a bit -- not having heard of more than 30% before.

gone fishin
03/07/2015, 07:47 AM
I agree a 100% WC IMO is a drastic response to a severe problem such as a chemical spill. Good luck on your build.

tmz
03/07/2015, 09:55 AM
The ammonia oxidizing bacteria and denitrifying bacteria colonize surfaces ; some move in the water and settle on new areas but most are set on surface area;so, a large water change does not diminish the biofilter if the surfaces are not allowed to dry . Large changes do take out organics and major minor and trace elements ,though, as well as adding back elements. I prefer smaller routine changes to promote constancy in the aquarium chemistry and biology.