Water changes...

[ReefTECK]

I've determined that I am performing 7% weekly water changes on a moderately stocked 120, 137 gallons total system volume. The predominately SPS system includes an 8 gallon refugium and 8 gallon sump, 1 gallon moderately decent skimmer. (I'm going to get a badd *** skimmer soon)

Parameters seem fine, but...does this seem adequate?

 

[StrategicReef]

I am changing 7/100 I found it working very well, key is to do it weekly on time.
Less shock to the SPS