I cannot speak to the scraper you mention but I have tried lots of them. I found that the best thing by far for me is to get a piece of 3/4" SCH 40 PVC and cut a notch about 1/2" deep in one end with a hack saw for a standard razor blade. Then put the blade in at about a 30 degree angle to the pipe.
This thing will scrape off coralline in one pass and you can easily replace the blade every time to avoid rust entering your system. Total cost is like $3.00.
I made one in 5 minutes and bought a lifetimes supply of blades.
I use the one sided razor blades that have the metal support thing on the non-sharp side. It's the kind that goes in those hardware store scraper gadget things for scraping paint, etc. Well, if you use a hacksaw to cut the slot in the PVC pipe it will be slightly thinner than this support portion of the blade. This will allow you to slip the razor in from the side (with pliers, be careful) and it will be very snug once in there.
You could use a drop or two of super glue if you had to but I have found that it is not needed. All the force during scraping is to push the blade in farther and none to pull it out.
