Aragocrete [DIY Live Rock]

[suckafishtankcleaning]

Sorry that it has taken so long to put this article up. But here we go...

First you need to get your supplies together:

• Sand for your molds [ I used playground sand because its cheep and not going into the mix. But you will need a lot of it depending on your mold's size]
• Something to hold the sand mold. The size of this will depend on the size of rock you want to make. [ I used 15"x30" cardboard box with a trash bag to seal in the sand. I now recommend small Rubbermade container about 13gal]
• A bucket for mixing and a tool to help you mix
• Portland cement^ any type will work. I would go for what you can find in the color you like. gray/white [^PC]
• Aragonite sand* and/or crushed coral** [*AG **CC]
• Trashcan or anything that works to hold water and cure the aragocrete

There is a couple of ways to make your rock mix. The typical method is a 5 to 1 ratio of filler to concrete [I will talk of different mixes later]. Now for the filler you have a couple of options. First you could do all AS and concrete, but this makes a very heavy rock that is not very porous. Or you could do all CC. Personally I didn't like the look of that. I use a combination of the two. A mix that I liked was 3 parts CC 2 parts AG and one part PC. You need to just mess around with different combination to find out what you like.

Depending on the type of rock structure you are trying to make, you may want to change the ratio of filling to PC. For example, if the piece is going to be thin it needs have a higher concrete ratio [i.e. 7 to 1]. I found myself using a 6 to 1 ratio for the majority of my rock work. It helps to keep in mind what type of piece you want before you even make the mix.

Time to get dirty. Start with making you sand mold. Fill the container with moist sand. It should be wet enough to hold its self up but not soaking wet. I found that the more random the mold was, more it seemed to look natural. Remember to leave some moist sand off to the side, to cover the piece when you are finished.

Once you have your mold ready mix the dry ingredients, whatever ratio you have decided on. Then start to add water, slowly. Some say that is one part water. At times I would have to use more depending on the mix. This part is a little tricky you don't want it to be dripping wet. However, you don't want it to dry either. Its safer and stronger to have it a little more wet side then dry side. This is because the bonding molecules need water. To test it take a handful of mix, it should hold together for the most part. But you don't want it to be a soupy muddy mix. It takes a little practice.

Go ahead and start adding the mix to your mold. Get creative here! I go with the flow, I work with just a basic idea of what I want. No more then that, be free to change your idea up. There are a couple of tricks to make the rock work have different features and a natural look [that was my main concern, fake looking rock]. One is building up sand over a patch of mix, then adding mix over the sand [remember the mix needs to touch other mix to hold together. the sand helps to hold space, make voids] to make an arch or a tunnel. This can create a space for a cave or whatever you can imagine. Another trick is to use random objects create voids. Like I said get creative your brain is the limit... Once you have finished filling the mold use the moist sand we set aside to cover your masterpiece. A thick layer is good idea. The moisture will help to create a stronger bond in the concrete.

Give the newly formed rock 48 hrs to set up. After you remove your rock from the mold rinse it down and move it into your curing tank [trashcan, whatever you want to call it]. Change 100% of the water at least every other day for 5-8 weeks, its a good idea to move the rock around too. It takes concrete 30 days to reach its full cure. Till that time the rock will raise the pH of the water while it cures. After about 6 weeks test the pH of the holding tank. If it is the same as your tap water [and yes use tap water for the curing process] change the water once more, and wait a week. If the pH has not increased then it is ready to start the live rock curing process. If the the pH did increase you will want to change the water and try another week. At this point you can consider your aragocrete to be base rock.

*****warning******
Be careful adding this to an existing tank. Make sure that the rock as fully cured, otherwise it can kill off your tank


You have now helped to save the reefs around the world, and saved your self a little bit of money. Have fun and be safe, wear gloves. I hope this helped.

[LCP136]

Good read. K+.

[grubbsj]

Good description of the processes, any example photos of the molds you have made and what the finished product looks like?

[suckafishtankcleaning]

Originally Posted by grubbsj

Good description of the processes, any example photos of the molds you have made and what the finished product looks like?

yeah here is the thread with some pix:
DIY LR pix

[Russter]

My rock has been going for 7 weeks now and the pH is still off the chart. I change the water every couple of days. I made it with crushed oyster shells and portland cement with a little bit of sand. Do oyster shells take longer to cure?

[Matt Rogers]

Originally Posted by Russter

My rock has been going for 7 weeks now and the pH is still off the chart. I change the water every couple of days. I made it with crushed oyster shells and portland cement with a little bit of sand. Do oyster shells take longer to cure?

Mine took a long time too. I was using a kiddie pool. How much water are you using?

[Russter]

Well turns out I could have had this rock in my tank alot earlier. A thin layer of white stuff built up on the inside of my garbage can, causing the water to read high pH all the time. I switched cans and the pH was around 8.2 for a week so into the tank it went. Ph in DT hasn't moved and rock has been in for 2 weeks now.

[grubbsj]

Good follow up, thanks.

[horkn]

I am thinking I will make my own DIY LR as well. I will need some funky shaped pieces for my upcoming 190g (maybe more) build.

[Reefrubble]