Ok, from my understanding, the point of using the venturi on the intake is to have the air bubles in the pump to be whipped up by the impeller (iddealy a needle wheel) however, if you're not using a needle wheel impeller, there is not a huge gain by having the venturi on the intake,
in fact, if you get to much air in the impeller chamber at one time, the impeller will lose resistance and this will cause the motor to temporarilly spin faster which will a) burn out the motor over time or b) cause bits and pieces of the impeller to break off (like hitting water at high speeds, it can hurt).
This is what ive learned over time from the pump people. I do not believe a venturi will ever do this in the proper circumstances, but i like to be safe.
but yess, its the venturi itself that creates the bubbles, if you do not know what it does, it pinches the water flow right before the air inlet, this creates somewhat of a vacuum with the water rushing past it, this creates a nice frothy foam. Not as frothy as if you had run that foam through a needle wheel (ideal).
If you have a regular impeller,
IMO, it will not do much for the bubbles, and by running it on the return of the pump, you get more water flow out of the pump, less sound coming from the pump, and ultimately, more bubbles (faster flow through the venturi=more bubbular-type vessles)
So yeah, to sum up this long-winded explanation, all a needle wheel impeller does is whip up the already frother venturi water, if you don't have a NW impeller, no need (in my eyes) to have the venturi in the intake.
Hope this helps
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Josh Small Frys 120 Fish- 2 Percula Clowns, Hippo Tang, Flame Hawkfish, Black fin Shrimp Goby
Coral- Green and Pink Frogspawn, Colt Coral, Zoanthids, Green Acropora, Fungia coral x2, Millipora
Clams- 1-4.5" Crocea Clam, 1-6" Maxima Teardrop
Cleaning Crew- 2 Skunk Cleaner Shrimp
2 Peppermint Shrimp ,20 Tiger Trochus, 5 Blue Legged Hermits
RIP Victims of the massacre :
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