By merging fluids using space belts it's possible to make a fluid catcher catch (at least) 2 fluid launchers worth of fluid while the fluid launcher and fluid catcher indicate having the same throughput.
In the first example (see 1st attached video) they are able to supply 16 painters which indicate needing 450L/m each for a total of 7200L/m while the fluid catcher says it only has a throughput of 1800L/m or 3600L/m for 2 catchers.
In the second video I'm able to supply 24 crystal generators (needing 600*24=14400L/m) with only 4 fluid catchers. (indicating to be able to supply only 4*1800=7200L/m)
I expected the belt to fill up because the fluid catcher's throughput can't handle the speed of the incoming belt, yet it seems the fluid catcher has a higher throughput than indicated.