Sounds like a good idea, the tank's CO2 system will be more responsive certainly.

I'd suggest at least 300gph running through each reactor, a bubble counter for each reactor is a good idea truthfully.

You can measure the rate easily this way vs adding 4 bubbles/sec through one, it's easier to measure 1/2 that rate.

You can crank up one high also, then tweak with the other reactor.

Note, you will need 2 needle valves to run two separate CO2 reactors, the flow will not go to both of them equally.

Regards,
Tom Barr