Hydraulic cement crumbling months later

[shollis2814]

OK, so I built a rock tower and used a driveway reflector rod, some putty, and hydraulic cement. I followed all instructions on the container, let it air cure for longer than the allotted time, and then bucket cured it for over a week until the kH and pH were no longer fluctuating. It's been in my tank for a while now.

Some of the hydraulic cement seems to be flaking or crumbling and turning a light gray. Has anyone else experienced this? It does not seem to be affecting my chemistry, unless somehow that could turn into a magnesium sink. Corals are healthy and growing.

 

[Broadfield]

Yep, I had this same exact issue with the same exact product. If you use the stuff from Marco Rocks you will have zero issues. You can read more about my issue in my build thread... here's the direct link to about a year ago:

https://www.reef2reef.com/threads/b...build-ocd-inspired.211616/page-3#post-2652495

 

[shollis2814]

Thanks. Do you think I can go over the weak spots with the Marco stuff or do I need to do a total breakdown?

I have some frags on plugs I was hoping to encrust some shelves. Looks like I need to break this down soon.