Coralline grows on glass, but not my rocks.

[T-J]

I’m curious, why does coralline grow so well on my glass but not on my rocks? I want it on the back glass, but I have to scrape new coralline off my other three panels every few days.
I’m just not seeing it on my rocks. SPS corals grow just fine. It grows on the glass fine. So I know conditions are right.

 

[ZoWhat]

What's the lineage of your LR? Did it come from the Ocean? A River? A hole in the ground from Texas? Lol

My LR is all ocean rock except for one piece the seems like it's river or earth rock. Not much wants to grow on it except for zoas

 

[HB AL]

Any asterina stars eating it on the rocks? I had them explode in population and devour most my corraline then went down in #s and the coraline started back, in a way I dont mind them eating coraline off rocks some as it keeps them from clogging up.

 

[Waters]

My tank has the same issue......I believe my two urchins are just cleaning it off the rocks as it grows.

 

[davidcalgary29]

Your LR is probably already populated by other algae, and there likely aren't that many footholds for coralline to gain at this point. I note, glumly, that I have a coralline explosion on the front glass of my IM40 -- and no where else -- as it's the one tank surface that's free of other types of algae.

 

[Timfish]

Light intensity is a factor also. The various species have different light requirements and many will not grow in intense light.

 

[davidcalgary29]

I meant to write "already populated with algae and bacteria". These early mornings...

 

[Screwgunner]

I am 6 months in and have the same problem . Bare bottom is covered back glass and sides have it to . One little spot on one rock is all I can find. It is getting bigger.

 

[hawk82]

Funny I have the same thing in my tank. Covers the glass and anything plastic in the tank, but never on any new rock I add.

 

[RSnodgrass]

Another logical conclusion is that coraline thrives in two conditions (other than elements)... low light and high flow.

On the sides of tanks there's lower par and (usually) higher flow directly contacts the surface of the glass.

 

[T-J]

Another logical conclusion is that coraline thrives in two conditions (other than elements)... low light and high flow.

On the sides of tanks there's lower par and (usually) higher flow directly contacts the surface of the glass.

That wouldn't explain the other non-rock surfaces throughout the tank that are covered.
I think someone nailed it earlier that the biofilm on the rocks may be preventing it from growing. Only now am I starting to see spots of it starting to grow on the rocks. Might just be part of the dead-rock maturing process?