I would imagine the CO2 diffusion would be good from that. I do suspect it is for internal use (ie inside the tank), and it would be a bit of an eyesore if that's the case! Could be wrong though. It would be an amazing price for an external reactor.
i brought one about 4 months ago for my 260l i was runing about 3 to 4 bps and i found that it midway thought the day it bilt up wiht co2 gas,looked pretty ugly in there as well,i wouldent buy one,i just bought a aqua medic 1000,great bit of kit,not cheap thought,