I have no desire to go with a external controller of any kind.
My thought was to use a pair of L2's on opposite flow patterns like was previously suggested, before I side tracked this thread.
I can certainly see applications where a red dragon or abyzz pump would be called for, but on a closed loop where there’s no head pressure to overcome (though there is some friction back pressure of course) something much less expensive is really all that’s necessary. That the vectra has the ability to vary flow makes it almost ideal for a closed loop. I bought my M1 on the day it was released and it has hummed along (fugurative not literal as it is silent) ever since - 4 years, maybe even 5?
Just a suggestion to save some money, a $200 basic controller and a $200 module is much cheaper than taking a serious hit on two Red Dragons and replacing them with Vectras. Now that was all assuming you had 2 Red Dragons @mfinn