The pump utilized in aeroponic systems must be matched to the total volume potential of all of the systems misters.

A pump with considerably more output than the misters are capable of emitting will experience excessive back pressure, possibly leading to premature failure.  A pump with too little output will not supply enough volume for all of the misters to perform correctly, and may lead to clogging.

The pump is the heart of the aeroponic system and not a place to cut corners.  It must be reliable and readily available should a replacement be needed.

Submersible pumps are more easily plumbed and are placed into the reservoir.  The high volume of nutrient cycled through the misters eliminates the need for an aerator in the reservoir.

The pump needs its own timer.  An adjustable recycle timer is clearly the best choice.  When cuttings or seedlings are placed into the system they need a more frequent misting than more mature plants with highly developed root systems.

Mature plants (having roots that reach the bottom of the grow chamber) can be misted less often.  The root mass will inhibit the drainage of nutrient.  It is important to extend the "off cycle" so the nutrient will fully drain off.  Generically this would be called an adjustable recycle timer.  I recommend the ART-2 adjustable recycle timer.