The sponges that are supplied with this unit are simply not fine enough for the media most often used by aquarists in sa. Think about it:
3-5mm media (not much bigger than the holes in supplied sponge), abrasively fluidised, reduced pH........... you gonna get chips into the impellor.
Use a hailea pump, also 1000lph fitting (I suspect same pump as octo, or at least same factory)
Another problem which happened to me, is gas buildup in the top of the reactor, preventing water from flowing to the pump, i.e. pump running dry............
This will occur if you have your pH probe situated remotely from the reactor. As the line is blocked, the pH at the probe rises, switching on the CO2.......
I have the older unit, so no space for a pH probe, and have been trying to source a new lid (with pH probe holder and bleed line) for some time with no success.......