Annoying issue

[TodaysTrolling]

Yeah, not unconvinced that having a solid exterior on the rock is limiting bacteria colonization. especially since I have a shallow sand bed. Have the marco rock in the sump, May let it seed and also deepen the sand bed some. Sand bed is only maybe 1/4 inch thick. MAYBE 1/2 inch.

 

[jabberwock]

I think the issue with the rocks is that they are a vacant canvas. Same with Marco rock. This is not about bacteria, it is about empty fertile ground for algae to populate. I bet your bacteria population is fine. You just have all this open fertile ground (virgin rock surface) for algae to take over.

 

[jabberwock]

Ask me how I know...