The drinking water pump transfers drinking water from your reservoir into your tank, and an overflow siphon delivers new water through the tank and trickles it more than the biospheres just before it collects back again from the reservoir. Considering the fact that this is a preset heater, I recommend https://best-fish-tank-essentials49258.ziblogs.com/37192068/aquarium-filter-guide-uae-for-dummies