How much water should I be changing and how often , I feel like the standard response is going to be 50% weekly which I’m almost doing I do about 30-40% weekly but I feel my bio load isn’t that high and maybe wiggly under stocked my tabk is 500l and stocked with 4 eba 1 Oscar 1 sailfin pleco all juveniles running a fx4 filter , , with that stocking in that tank could I maybe do less water change?