IMO, in a tank with LR, these pads do not have a significant role in the biological filter, and you should be able to clean them frequently....meaning every few days, even in tap water. This will kill the bacteria, yes, but if you have significant live rock (actually...I don't see an amount of Live Rock?), a refugium, or a wet/dry, etc, these pads should be negligible in terms of their contribution.
I think there is a greater benefit, personally, to rinsing them much more frequently, then only doing so at a water change. They do play a significant role in the tank in terms of being a mechanical filter. If you do not use these pads, then the gunk they trap gets carried elsewhere, and may still cause problems.