Ceramic clay structures

[Clemo1971]

Hi

im looking for a ceramic clay media or something to make these rock structures for my marine tank so it needs to be waterproof yet porous I’ve attached some a photo of what I mean any help or advice would be greatly appreciated 

[Sorcery]

If you can't get Standard 101, look for another modeling clay, something that gets fired in a kiln to finish.  

Fired at a lower temp than recommended usually leaves em porous, but you can add "openers". These openers can make the clay easier or harder to make your shapes with.

Sorce

[Min]

@Clemo1971, if you can find dry sea sponge that is about the shape you want you can dip it in slip, let it dry then fire it. I used a torn off piece of natural sponge from the dollar store (sold for painting effects on walls) for the little piece below. Porcelain slip, clear glazed after bisque firing. This isn't a very good example of it, I had some better pieces but I didn't photograph them and now they are gone. The sponge can be torn into shapes, dipped in slip, dried and fired laying flat if no glaze is used so you could get more of a tree like shape as in your example photo.