Apisto eggs layed on substrate?

[FabianUlSua]

How common is for apistos to lay eggs on the substrate?
This has only happened to me twice, the rest of the time they lay them on the roof of the cave.

 

[MacZ]

Rather uncommon, but depends on the species.

 

[yukondog]

I've never had them lay on the sand, but have one that every now and then lays on the glass behind the filter.