Soldato
Should be fine as long as the Aquaero is only seeing the rpm signal from one fan. It'll work if it sees all of them; it'll just be a randomly fluctuating useless figure given for the rpm. Also worth making sure all the fans are the same - fair assumption they're all spinning the same with the same input that way.
You may not need the molex powering the splitter as the Aquaero can supply enough power by itself.
You may not need the molex powering the splitter as the Aquaero can supply enough power by itself.