Why is it that the consensus is that for smaller tanks a skimmer is deemed optional or not even necessary? Almost everyone I spoke to say to me, why bother or save your money. The answer seems to be do water changes and all is fine. Well, maybe I"m not understanding things as I thought, but no matter what size the tank is, water changes should be done anyways periodically, and just as well the benefits of a skimmer delivers the same no matter what the volume is of the tank? So why smaller tanks don't require a skimmer?