Water changes for a refugium tank

[yamba]

I am planning on upgrading my 5 gallon tank to one with a refugium around christmas time. I was wondering if i do this do i change 10-20% of the tank volume including the refugium each week, or just that of the main tank? I assume it is the percentage of the total volume but thought i would verify this. thankyou for any help i would appreciate it.

[Pikelet]

Percentage of the combined volume of water in both tanks, correct.

[printerdown01]

The 10-20% ratio is a large varience anyway... I have a 12 gallon tank with a 2.5 gallon fuge. I do a 1 gallon change every 2 weeks (approx). Now if you have a 5 gallon tank, and are going to add a 5 gallon fuge, which would double your volume, you could most certainly consider the new volume. But if you are going to add 1-2 gallons, I don't see a major difference. It is true that you will have more water, but it is also true that they system itself will be more stable with the addition of the extra LR, LS, and increased water volume than it was origonally. So IMO either way would work just fine! *personal note, I like doing 10% rather than 20% simply because it is less of a shock to the inhabitants.

[NaNO ReeFiN]

I do a 15% water change of the TOTAL volume of water each week, and that includes my refugium.