Interesting

[Barry Tetra]

So I have this cup outside that I use to cultivate Cryptocoryne crispatula var. balansae from seeds. Apparently, it developped this “iron zone” beneath the substrate. Very interesting, I now put it in my aquarium.

 

[GaryE]

Is it soil like, or is it the red algae type that forms under the gravel and on the walls of some tanks?

 

[Barry Tetra]

Is it soil like, or is it the red algae type that forms under the gravel and on the walls of some tanks?

I haven’t poke it, but I’m guessing it’s more like rust, like you know iron bacteria.