Live Rock Porosity

[GARRIGA]

Curious if anyone knows of a study where an established tank had sample rocks or ceramic media or matrix removed and sliced then placed under a microscope of enough magnification to confirm those pores are still functional vs plugged by biofilm? Current hypothesis by some that they aren't and I'm leaning that way. Thoughts?

 

[Dan_P]

Curious if anyone knows of a study where an established tank had sample rocks or ceramic media or matrix removed and sliced then placed under a microscope of enough magnification to confirm those pores are still functional vs plugged by biofilm? Current hypothesis by some that they aren't and I'm leaning that way. Thoughts?

I remember seeing a photo of a live rock that was cut cleanly in two. I think the point was to show all the nooks and crannies. I don’t remember any evidence about the change in porosity over time.

Just thinking out loud, the large pores, craters and entrances to passageways are likely to collect material if they are not regularly cleaned out. This might not totally clog them but flow and diffusion are likely to be negativel impacted. So what?

As for the tiny, < 1 mm size openings, I would bet they become slimed over fairly quickly in an aquarium where water flow is low. And if it is not the actual biofilm doing the clogging, its the stuff that sticks to the biofilm. I can also easily imagine a little sponge or cyanobacteria film cutting off flow to many tiny openings.

I can easily image that every surface and tiny opening is quickly “slimed” over in an aquarium. This might be OK though. The biofilm is likely to be a useful waste removal system. And I remember reading that denitrification can occur within biofilms that are not very thick, nor far from aerobic conditions. Maybe the presence of tiny pores is not so important after all.

 

[GARRIGA]

This question came about when Lasse brought it to my attention and further solidified at RAP during a conversation with Dr Hovanec where he showed me a customer’s biofilm although I recall that might have been caused by other issue yet still the point of discussion being how biofilm overtime clogs the finer pores such as found in ceramic media or that deeper inside porous rock.

That photo you saw had no signs of biofilm growing within the nooks and crannies?

Interesting point on the denitrification within biofilm. Not something I considered before.

 

[Dan_P]

This question came about when Lasse brought it to my attention and further solidified at RAP during a conversation with Dr Hovanec where he showed me a customer’s biofilm although I recall that might have been caused by other issue yet still the point of discussion being how biofilm overtime clogs the finer pores such as found in ceramic media or that deeper inside porous rock.

That photo you saw had no signs of biofilm growing within the nooks and crannies?

Interesting point on the denitrification within biofilm. Not something I considered before.

The photo I saw did not provide a detailed analysis of the passageways. I think you would need to stain the rock surface and view it under high magnification to show live bacteria were present, but that’s an educated guess.