2ft is ard 200l. Assuming u want to have ard 10 times changeover of water, u will need ard 2000l/h pump. If ur intention is to run the chiller and then to main tank, u have to determine the flow reduction from elbow joints in ur piping a and headlost. Seems like 5000 maybe the bet as 10000 will be too strong for yr chiller and if u reduce it to meet ur chiller, by the time it reaches yr main tank, flow will be weak.
Depending on ur setup, only then u know the dead spot and to add wave maker to ease off the dead spot. General speaking, one mp10 may not be enough. Hope this helps.