Should i swap the return pump on the 24 gall nano?

Answer:

Hi

The live rock rubble will create a more natural zone for organisms such as
Mysid shrimp , Copepods etc to proliferate within the rear section of the
tank so isnt a bad idea. There is no real reason to change the pump
with regards to adding extra flow through the rear compartment as in
effect you will be creating a refugium of sorts so a slow to medium flow
rate would be preferable.

I also wouldn't use rubble that is any smaller than golf ball sized pieces
of live rock as small bits could compact and flow may just take the fastest
route possibly causing anoxic zones.

The only real reason I can envisage for changing the pump for one with a
higher flow rate may be to exclude the possibilty of having to use another
small power head in the tank for extra flow. This carries its own dangers as
the aquarium will then only have one pump to rely on for flow, if the pump
were to malfunction while you were out the tank would have no other means of
water movement and oxygen levels would become very low over a short period
of time.

Hope this helps

Regards Tony