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Choosing a Main System Aquarium Pump
There are three critical factors
when choosing an aquarium pump: the desired flow rate, the amount of head
pressure and cost.
Desired Flow Rate The optimum tank "turnover rate" is, 7 to 8 times per hour for saltwater reef tanks and 2 to 3 times for freshwater tanks. To approximate a aquarium pump's flow rate in a closed system, subtract 25% from the pump's maximum rate flow to compensate for filter and plumbing restrictions. For example: using the multiple of 4 times per hour, a pump with a maximum flow rate of 375 gallons per hour (gph) would be appropriate for a saltwater fish-only tank of about 70 gallons ((375 * 75)/4)=70.31). If you want to be more exact about the degree to which the filter and plumbing will compromise the flow of the pump, you can calculate the head pressure, refer to the charts provided for most pumps. Head Pressure Generally, the head pressure is the distance from the inlet of the aquarium pump to the discharge point in the display tank. As the head pressure increases the gph will decrease. Along with the distance from the inlet of the aquarium pump to the discharge point in the display tank, a number of factors effect head pressure: *each 90-degree bend in the
plumbing will add about one foot of head due to friction.
*as a result of friction,
each 10-foot horizontal run of pipe will add a foot of head pressure.
*Any time a pump discharge is
shut off, perhaps to a protein skimmer, this will also rob the display tank of
flow.
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