No, this is not a test.
Just things to think about.
If you are using Filter Socks on your Over Flows.
How often are you changing them ?
How are you cleaning them ?
Filter Socks collect Detritus & Uneaten Food.
Even if these are changed on a Regular Schedule ( once per Week, Month, Year )
This can effect your Water Quality depending on a few factors.
Bio Load vs Frequency of Sock Replacement.
Drastic changes in Water Quality can have adverse effects on your Corals.
How do you clean the Socks ?
When you put them in the Washing Machine,
Do you use:
Just Water ?
Water & Bleach ?
What size Load do you use ?
Do you use the Second Rinse ?
I always use the Largest Load & Second Rinse, for 2 reasons.
If you use Bleach, It helps to insure the Bleach is rinsed out of the socks.
There may be Soap ( Phosphates ) residue left in the Washing Machine from previous Loads.
And the Large Load & Second Rinse helps to remove this.