DIY rocks

[ChloG]

I have been looking at old forms of making diy rock. I cannot get Portland cement where I am but I bought a bag of polyblend white sanded grout out of recommendation. It’s first ingredient is Portland cement. Has anyone used this? Thoughts?

 

[Flippers4pups]

Haven't heard about that product. If you can get your hands on technical data sheet on ingredients, that would be helpful. Main thing is elements known to be toxic to marine life. The other is will it though off your PH. I would be very cautious.