Parallel or Series?
 

I am new to water cooling and am wondering on how to set up the water blocks to get the best performance. Both of the water blocks uses 3/8" ID tubing. One idea for running the system is in series the other is running the blocks parallel to each other. Here is the parts that I have for the system.
Swifttech MCW50
Swifttech MCW6000-64
Black Ice Extreme 120
Danger Den D4 Pump
Danger Den Polyetheneline RESHDPE with 2 half inch in and one output

Always put blocks in series.

Not always, but mostly. IN your situation, series.

Thanks for the help. I am new to this so didn't know what to do.