Quick water change question

[Sexytang]

On my 36g I normally do a 5g wc once aweek if I don’t a few of my corals start acting up. I had saved up 15g of my old water and added it to my 14g biocube and have it running through carbon and polyfil has been for 3 days now. Could this water be ok to do a 5g wc on my display tank again till Friday when I can get new water.

 

[sde1500]

You want to use old water from your 36g, that is currently in your 14g, to do a water change in your 36g? I'd say no. Defeats the whole purpose of a water change, be it for nutrient control or chemical balance.

 

[Kaludar]

I mean it’s not going to hurt anything to put it back in there but it’s not a water change, unless the water is fresh so you might as well not do it.