DIY "Live" rock


I was looking through some of the DIY pages on this site, and noticed that there wasn't one yet for making "live" rock for Saltwater aquariums. Even though there are sites out there that explain how to make your own, I thought I would start a thread for my fellow fishloreans.
This has been a project in the making for me for almost a month now. I have read many threads on other forums as well as extensively read through which I HIGHLY recommend that you do before trying this yourself. I have found it to be a very rewarding experience and I can make the perfect rocks for my tank that I know will fit.

-You can create your own aquascape with your only limit being your own imagination.
-You can create rocks that will connect together.
- MUCH cheaper than purchasing live rock, or base rock.
-You can also create your own reef plugs with slots in the rock to hold them.
-Rocks can potentially be much lighter than regular live rock.

- Very time consuming.
- Rocks must cure for AT LEAST one month.
- Rocks are not seeded and will take longer to become “live.”
- If not cured properly rocks could leech harmful substances into your aquarium.

Materials needed:

- Portland cement type I-II (Lowes $6.00 a bag)
- Crushed oyster shell (Abuchon 17.00 a bag)
- Scrap wood to mix cement
- Bucket to mix cement in
- Large Plastic storage container
- Styrofoam or cardboard box (use whatever you have on hand)
- Spray bottle
- Toothpicks or wooden skewers

The only thing that I needed to purchase was the crushed oyster shell available at any feed store, and the Portland cement. It MUST be Portland cement because it does not contain any rocks in it which allows you to control what is mixed in. I chose to use crushed oyster shell, however some people choose to use aragonite sand in place of the shell. It was cheaper to purchase the shell in my instance rather than buy the sand.
Now onto the rock making! There are many different methods to making rock and within that many different variations. So far I have only tried one method. I will be making more kinds in the future to see which ones I like best, so this will be a thread in progress.

Crushed oyster shell rock:

The Mold:

1. First start with a plan. Sketch out if necessary the types of shapes you would like in your tank, and how you might want to stack them.

2. Measure your tank if space is an issue, so you know what the largest size is your rock can be.

3. Now fill the Styrofoam or cardboard box at least 2 inches deep with crushed Oyster shell.

**Please note in the picture I used sand. You do not want to use sand because of the silica content, which means I cannot use my first batch of rock**

4. Moisten the shell with the spray bottle until it is moldable but not sopping.

5. Now carve the desired shapes into the crushed coral keeping in mind that this is only half of the mold and a general outline.

The mix:

** Please note that this is not an exact science, and it is more like making bread dough. If it’s too dry add more water. If it’s too wet, add more cement. If it’s too smooth, add more shell. The mix will differ depending on the weather.**

2 parts cement
2 parts crushed shell

6. Mix cement and shell together. Add water and stir until the mixture is wet and gloppy, but not soupy or crumbly.

7. Now pour mixture gently into the mold being careful not to collapse the sand. Do not press the sand in the mold. The unevenness of the mixture in the mold is what gives the rock its character and naturalness.

8. Now take some shell and gently sprinkle over the mixture until it is completely covered.

9. Spray the top until moistened.
Now for the hardest part…THE WAIT. Do not attempt to remove the rocks for at least 12 hours. 24 would be better though, spraying the top of the container periodically with water because cement cures stronger when it is kept moist.

After the 12-24 hours dig up your rocks and rinse them off under water. You will be pleasantly surprised at how nice they turn out. After you rinsed them and had time to admire them, place them in the plastic container and fill it with water. Try to change the water daily and test the pH on a regular basis. I have read soaking them in white vinegar for a couple days will speed up the curing process, but have not tried it personally. When the pH returns to normal your rocks can then be added to your aquarium. Mine are not at this stage yet, so I don’t know the exact time frame, but have read anywhere from 1-2 months.



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The rocks...


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2nd batch

Here are some pics of my second batch of rocks, as well as a picture of my other rocks curing. I really like the look of this style of rock, and am toying with the idea of making a bunch of stackable ones for my 30g, but I wanted to see how these came out first. I read that to add holes in the rock for beneficial bacteria to live, to pierce the rock with skewers. I didn't have any skewers so I used toothpicks. I'm not sure if I like the look of the rock with the holes in it because it makes it look more man-made.


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It looks interesting but not something I would do. I don't think you can achieve the amount of surface area real live rock gives you, and it doesn't look very appealing to me with those big holes in them. Good luck with the project though.


Well, making it is my only choice, because the live rock selection is terrible where I live. Every rock seems to be round and heavy, and for live rock I would expect more growth on it.


Well, making it is my only choice, because the live rock selection is terrible where I live. Every rock seems to be round and heavy, and for live rock I would expect more growth on it.

Yeah, glad your being creative. Have fun.


very nice might do this myself if I start....when I start my over 300g tank for the base rock.

GARF (geothermal aquaculture research foundation) is a very interesting group. They have many ideas, and great information. Also great corals GARF BonsaI ;D have two of them


i've heard of some one adding coarse salt to the mixture, which after being in a tub with small pump pushing water through it, dissolved all the salt inside until it was very very porous(checking salt left via salinity meter) after it reads no salt, do an extra 2 or 3 days to make sure and then you have very porous rock!.... I saw somewhere on youtube


yeah I saw that too! I was actually going to try that next when I have some free time. I like the style of the last rocks that I made, but they look too fake to me. SO if I can make them more porous with the salt but the same way I think it would be perfect. At any rate those last two rocks would make ok base rocks at the very least.


I kinda liked how your 2nd batch turned out... you could put some coral on that, no?(I'm no Saltwater expert lol )


Thanks! I was thinking of making them all like that so that I could just stack them in the tank and get nice height without me worrying they will fall over and kill something. Plus this tank will be moving a lot in the future, so I want something that will be kind of easy to put back together. I want to make them with big holes for reef plugs.

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