Elatine Hydropiper carpet

[M.Aurelias]

I have a modest 40L low tech, the substrate is black stone (avg 4mm dia) with out any soil or additives. To grow something like Elatine hydro would I need to top the substrate up with something, or can I plant direct into the gravel?

 

[viktorlantos]

To grow the real elatine hydropiper you need small grain substrate. As this plant has small and very dense root system.

Green Aqua Showroom by viktorlantos, on Flickr

 

[M.Aurelias]

Never seen it like that, thank you. Does the substrate need to very thick? I am thinking I could add sand in areas for this to grow, or perhaps even put an entirely new layer on top of my existing gravel.