Do you recommend shale is an aquarium with Mollie Swordtails and Cories. If absolutely not what type of rock do you recommend? 
Shale
- Thread starter friendorfoe
- Start date
For the most part, you can put any type of rock with any fish. The exception is for fish that rub against the bottom and rocks. If you have any fish that will rub against the bottom, than avoid lava rock and other rocks with a sharp grain to them. You might also be careful that none of the rocks in your tank have overly charp edges.
I would put every rock through a vinager test first... if it fizzes/discolors the water... throw it out