best concrete for DIY rock

yea i always new there was some kind of chemical reaction to cause your ph so i know better to keep it cured for a time period.now if typeIV is faster ill try and find me some but ill probably leave it curing for a months or longer instead of just 4 days.

i dont think i need 100lbs its only going into a 75g. i also figure between aragonite sand and crushed oyster shells i think thats gonna add weight and increase the volume size of the rock but good info to know

 

I really hope you see this before you buy anything! but I made a mistake...
Just looked in the book to double check on it and type IV is actually low heat cement which means that the reaction will actually take much longer. (this is the kind they used in the Hoover Dam in 1931 and it is still curing to this day.)

You want type III which is the one I meant to mention earlier... type III is the high early strength one so it will harden very fast. Good luck finding it though, only about 3% of the total cement made a year is processed as type III and it is more expensive. You may be able to find it at a local store or ready-mix supplier. We are a ready mix supplier and we dont even handle it. (to make our high-early concrete (aka type III) we put in about 3x more type II portland cement into a mix to facilitate the reaction faster.) <-- this will make your concrete be VERRRY white, like as white as you can get it... lol

Edit: if you mix it with 3x the type II cement just make sure to add your water and sand slowly, otherwise you will have a slush with lumps of cement in it. Note: It will still take the 120 days to cure completely but will be bleach white within 24 hours.

 

thanks good to know this tomorrow ill work on finding this.

 

I have messed with concrete before. You may want to try adding a few drops of dishwashing liquid to the mix. This adds air bubbles into concrete for outdoor use. Just a suggestion, I intend on doing this if/ when I get around to making LR.

Good luck.

 

With the prices of Live Rock at the LFS running from 5.99 a pound to a ridiculas 11.99 a pound, we know all too well just how expensive stocking a tank with Live Rock can be. If the price aint enough to break your back, consider how long and hard you got to dig through dealers tanks searching for that just right shaped piece! Then there is the issue of exploitation of our oceans natural resources making the harvest of Live Rock detrimental to our oceans reef. Now Im not much of a “Tree Hugger” but I do try to be responsible and use captive grown corals/fish when possible to minimize over exploitation of our reefs. Having been is the south pacific tropics for a number of years Im all too aware of the damage often done and the scaring that takes decades for mother nature to repair. While we can often times buy captive bred fish and aquacultured corals, aquacultured Live Rock isn’t as readily available and pretty expensive when it is. What can one do to get around this issue, get the Live Rock we so desire and be part of the solution instead of part of the problem? Why not make your own rock?

That’s right, make your own rocks! Its easy to do, and its very cheap to do as well. Not only is it a very viable option, its sometimes a better option as you don’t have to take what you get shape wise from the LFS when buying Live Rock but you can make your rocks to the exact size and shape that you want. Making rocks with Caves and Ledges aint nothing but a thang and your only limited by your imagination. Cheap? You bet!!! Agrocrete…as GARF refers to this home-made rock, can cost as little as .10-.15 cents a pound VS 6.00 a pound for even cheap garbage available at LFS. Using the recipe I will include here you can make a 5 pound rock for just 75 cents!!! The same rock of Fiji would cost about 30.00. For about 20.00 bucks you could do enough rock to fill a 75 gallon tank! You just cant hardly beat a deal like that.

How does this rock compare to “real” Live Rock? Well it can be quiet dense and it can be fairly shapeless texture wise. These are all issues that can be over came though with some creativity. I have made some 20-30 lbs show piece sized rocks that were so porous you could pour water through it almost as quick as pouring water through a screen. It doesn’t have to be as lifeless as a blob of cement either. Take the recipe I give here, follow some of the tips I provide, use a little of your own creativity and you can make some really nice looking rocks to defray the cost of setting up your tank and give up nothing in asthetics in the process.

There are some down sides though as there are never any free rides in life. You need to exercise extreme care in choosing your cement mix as most all of it has Aluminum in it and this is a bad thing for SW tanks. The recipe that I use calls for Portland Type II cement mix and it does have some traces of aluminum in it but I have yet to have a problem in my tanks nor has anyone else I know. GARF has been using this in their tanks for years and have reported no issues. But there is the possibility, so be advised. The rock you make can be made in a matter of minutes, which is great! But it will take about six weeks or more in fresh water that is frequently changed in order to “cure” leeching out the lime and other caustic compounds that will kill off your tank quickly if added too soon.

So lets get down to business! First the recipe…

1 part Portland Type II Cement
3-4 parts Crushed Oyster Shell
Water

* Use just enough water to create an oatmeal consistentcy…not too thick or pasty and not too runny or soupy looking.

The Portland Type II Cement can be obtained at any hardware store. Its pretty much a no brainer. A 90 lbs bag will run you about 6.00-7.00 bucks a bag.

The Oyster Shell can be purchased at the local feed store. I suggest this as opposed to Argonite sand because its so much cheaper and it often leaves a nice texture to your rock. Like Argonite and calcium based sands Oyster Shells are composed of calcium and other trace elements which will provide a degree of buffering and as it slowly disolves it will release calcium, strontium, magnesium and other essential trace elements to your tanks water. A 50 Lbs bag of this can be purchased for just a few dollars more than the cement.

Next is the tools of the trade. ..

1. Mixing bucket.

I prefer to use a 5 gallon bucket or one of those 3 gallon mop buckets that can be found in the cleaning section of the grocery store.

2. Mixing Utensile.

This can be something as simple as a large metal spoon, garden hand spade or as elaberate as a mixing attatchment for a power drill that’s commonly used for mixing paints.

3. Rubber Maid Tote or Styrofoam box

A fairly shallow Rubber Maid tote or a shallow Styrofoam box which your LFS is probably all too willing to give to you so they don’t have to haul out more trash will be needed to form your rocks and remain there for the 24 hours or so that they will need to set up solid. It needs to be fairly water proof in that you will want to keep the sand and rock in there moist and damp (not wet) while the cement sets up so that it will be strong and solid and not crumble apart easily.

4. Tub or container to soak your rock in

I like to use 5 gallon buckets for small pieces or frag plugs. For larger pieces I use a 55 gallon plastic barrel with a valve to drain it, but any suitable size container that’s plastic and heavy duty will work. You will be soaking your rocks in this container for at least 6 weeks or longer until the Ph of the water is less than 8.2 24 hours after the last water change.

5. PPE (Personal Protective Equipment)

You need to get some rubber gloves and some safety Goggles and a dust mask and more importantly, actually use them! Late Breaking News Flash…wet cement is caustic when it becomes wet. If you get any on your skin wash it off ASAP! Failure to do so even though you cant feel the burn will result in painful chemical burns to your skin that you will most definitely feel a couple of hours later after the fact. Wear those gloves! The safety goggles are for protecting your eyes. While they make replacement eyes, they don’t work nearly as good as the OEM ones you were born with, if you know what I mean. The dusk mask is to prevent the dust you might create mixing the cement in the bucket with your other ingrediants. While this dust is not wet and wont give you chemical burns, your nasal cavities and lungs are moist and the dust will absorbe this moisture and you will then have wet cement and get chemical burns throughout your respiratory system and this can prove life threatening if its severe enough. Do not under estimate the seriousness of the safety aspect here. I remember when stupidity used to hurt…there was a lot less of it back then!

* Im sure there are a gazillion other tools one could use, these are just the basics. Feel free to add more as you see fit.


Okay, now lets get busy!

1. Mix the Cement and Crushed Oyster Shell and Water until the desired consistency is achieved. I would suggest making small batches as you have about a 30 minute or so window to work with before the cement begins to “set”. You can always make more in a mater of a couple of minutes if your project is that ambitious.

2. Spread some crushed Oyster Shell in your shallow container and have some more standing by if needed to aid in shaping the rock you are making.

3. Scoop out some cement and begin forming your rock. It helps if you revert back to your pre-school days back when you played around in the mud and made “mud pies” and such, cuase your essentially doing the same thing again, your just a lot older this time.

4. Once you have made your rock, I would suggest that you add additional crushed Oyster Shell till its covered as this will not only help your rock hold its shape until it sets up solid but you can also dampen this material to hold the moisture while your rock sets up solidly. You might also find it helpful to mist this with a spray bottle periodically.

5. After you rock has set up for 24 hours, its usually safe to remove it and check it to make sure that its hard and solid and doesn’t crumble apart in your hands. If it passes this test its ready for the curing process to leech the lime out of it.

6 To leech the lime out of your rock you will need to soak it in freshwater. The length of time this takes can vary considerably on how dense the rock it, how large in mass it is, and the volume of water its soaking in. You will need to change the water frequently during this time. I will usually change water once a day for the first week and then scale back on water changes to 2-3 times a week. Generally I have found that 6 weeks is a good time to start checking the PH of the water its soaking in and when the rock can sit in water for 24 hours minimum and remain lower than 8.2 in Ph then you can probably use it in a tank at this point without issues. If you rush this process and add it to your tank too soon your Ph can easily sky rocket off your test kits scale!!!

Tips and Ideas

To make your rock unique, create more surface areas, and ideas for molding and shaping it try out some of these suggestions…

The Glove Cave;
To create this unique piece you can take some of those cheap dish washing gloves and inflate them and rubber band or knott the wrist end of the glove. Place it on the surface of your substrrate in your shallow container. Then spoon over it with cement leaving the knotted wrist part and the finger tips in the glove uncovered and sticking out of the wet cement mix. When this sets deflate the glove and pull it out from the cave you have just created

Fused branch type Rocks;
Can be created using a couple of different methods. One cheap way I like is to get some of those long skinny ballons and partically inflate them and then twist and tie them creating a cluster as if you were a circus clown making something for a childs entertianment. Place it in your shallow container and carefully cover it up with cement filling in all of the nooks and crannies not occupied by the inflated ballon. This can create a spectacular looking rock for your tank.

Frag Plugs;
To make these I have found that using the small cups like you put catsup in at the Fast Food place to work excellent for small plugs and small shot glass sized Dixie Cups to work great for larger Frag Plugs. This is a great project for those of you out there that are fraging corals to swap or sale.

To create more pores;
Try adding Macaroni Elbows to your mix substituting it for 1 part of Crushed Oyster Shells. I know it sounds weird but when your rock finishes curing, the noodles will have decomposed and dissolved leaving behind cavities in the rock and pores on the surface of the rock. Cherrios and Sugar Puffs will do the same thing…please don’t ask me how I figured that out.

Plastic Shavings;
If you have access to plastic Shavings, adding these to your rock is a pretty cool thing to do. For some unknown reason Coralline Algae will colonize the exposed plastic pieces quicker than it will calcium based rock, go figure… But the bottom line is that it will get Coralline growing on your rock pronto!

Tips from Jman785

"Mix 6 parts Carib Sea™ aragonite sand with 1 part Portland #3 cement. I also add some plastic saw dust to the mixture for a texture. I also have found out that mixing in a little rock salt and then sprinkling some on the outer surface tends to make a nice porous rock for the finished product, try it for yourself, once the rock salt melts, the rock is left with a hole and you have a nice texture. If you have a pool supply shop near you, then you can buy salt pellets for Salt Generators which is a form of chlorinator. These pellets come in a range of sizes, but will definently be just as good as rock salt if not better. My father owns a pool store, so I have the salt pellets readily available for my use. So anyway take a box, preferrably a stryofoam box that you've received a shipment of fish in, fill with aragonite sand, the same that you made the mix from, dig trenches in the box to make the formations of the liverock, and pour your mix in and smoooth and round if you'd like, sprinkle some dry aragonite on top and let it dry for a few days. I soak the rocks in freshwater for a night, and then I soak them in white vinagar for 12-24 hours, and then rinse them with freshwater, but I have found out, that letting them sit in freshwater changed every day, for about 3 days fully cures them and can almost guarantee a nice cured rock. Make sure you frequently check the pH and make sure its at acceptible levels before adding it to your tank...keep changing the water until it has cured, or you can speed up the process by adding chemicals. Happy Reefing!"


These are just of few of the techniques others and I have used over the last few years to make my own rock, and rock for sale or trade. Just let your imagination run wild and do some experimentation and see what you come up with.

Now that you got your rock cured and have arranged it in the tank, its time to seed the rock so you can get it colonized with bacteria and coralline algae spores. This can be done by adding some small pieces of Live Rock and let nature run its course. You can take rock rubble and crush it up with a hammer and dump it in your tank or add some Coralline Algae scrapings from a friends tank and toss this in the tank and allow it to colonize your rock.

 

thats some smart stuff for pores i never thoght of the salt pellets 1+ for that one

 

You sound like a salesman. ;D Also, I would say that making it is more of an alternative to dry or base rock, not live.

 

Good info, thnx guys. what about portland type I? It goes for $10 per 70 lb at my local store.