I had the brilliant idea to give my server 2 pumps for redundancy.

eheim 1046 + aquastream XT

my first thought was to put them parallel but when i blew on the aquastream i noticed it does not block if its not running.
so when i put them parallel and 1 of them is not on, the other one will probably just pump the fluids back into the reservoir through the pump thats off.
so then i figured, i'll put them in serie.
thinking about it, it should work. but as often with thoughts. i probably forget something.
anyone with suggestions experience or something else that can help me?

(ps i do have some one way valves, but i prefer to not use them, cause they are pretty heavy to open)

i tried them redundant parallel.
the eheim pump is not strong enough so most of the coolant gets pushed back through this one.
adding a one way valve helps to prevent this, but now this pump is not doing anything and just getting hot.
so i decided to replace the eheim pump for a aquastream xt and put them in series.