DIY Rock Formula/Recipe

[Hermie]

Hi, I did some reading about DIY rock the past few weeks and after some experimenting and research I've settled on a formula for the rock I will be adding to my tank in a few months (after curing).

• 3 Parts CaribSea Aruba Puka Shell (large substrate approx. 3/4" per piece, whole shells etc)
• 2 Parts CaribSea Aragonite Sand (or any med-fine coral sand substrate)
• 2 Parts Sakrete Surface Bonding Cement - White (sifted to remove added fibers)
• 1 Part (or as needed) Water

So, the reason I am posting this recipe is because I could not find White Portland Cement anywhere near me (Southeast US) and the gray Portland Cements I used were totally too dark and "aesthetically yucky" looking, especially given the white shells and gravel used in the mix.

Instead of the Sakrete Surface Bonding Cement, I wanted to use Quikrete's Quikwall because according to Quikrete's documentation, Quikwall cement is rated for potable water which, according to my understanding, includes safe for aquatic life. Well, the Sakrete is the "sister" product of Quikwall, in that I believe it's the same product but it's made by Sakrete instead of Quikrete. I'm not 100% sure that it's safe for aquatic life, but I am 75% sure it's safe and I'm both thankful and willing to be proven wrong by anyone that could provide that helpful info with certitude. I'm also planning a month long cure so I'll have enough time to do more research and test the water in which the rock will cure.

Special thanks to
R2R, www.garf.org and www.ipsf.com
for their youtube and webpages on making rock.


Some pictures of the mix prepared tonight are attached

I'll try to update this thread as the rock cures and when I add it to a tank

 

[nautical_nathaniel]

Looks good so far! Be sure to make a build thread when you get all of the pieces in your tank!

 

[cdhappy]

Great ideas. Excited to see and learn about the project!

 

[Hermie]

Alright, update with a few tips:

1. For large/complex pieces try mix one big batch of "rock" and try to make the shape with one batch (you can always use epoxy to connect dry pieces later).
   
   
2. Use "props" to maintain the shape during drying/setting.
   
   
3. Try to "set it and forget it" in that the newly mixed cement needs to be disturbed as little as possible once you "shape" for maximum strength. That means a stiff platform on which to set the rock is needed, ex: wood, styrofoam. If you set it on cardboard and then move the box around a lot before the rock can set, it will weaken the shape. (you can always use epoxy later).
   
   
4. Updated Recipe (small changes in bold):
   • 3 Parts CaribSea Aruba Puka Shell (large substrate approx. 3/4" per piece, whole shells etc)
   • 2 Parts CaribSea Aragonite Sand (or any med-fine coral sand substrate)
   • 2 Parts Sakrete Surface Bonding Cement - White (sifted to remove added fibers) - Try not to use more than 2 parts cement
     
   • 1 Part (At most) Water, your substrate's wetness before mixing will affect how much additional water will be needed.

Needs to cure:

Pics from a new batch today, reinforced with plastic mesh sandwiched inside: