The aragonite concrete thing did however peak my interest, so back to the drawing board I went.  Many hours (o.k. Months) of searching the web for information, conversations with some masons, more than a few talks with the local water company lab techs and I decided to give my first real reef tank a whirl.  The first issue I ran into is the particular water quality we have here. Near 12 mg/l of Silicate and .2 mg/l Phosphate.  Yes, that is 12 and .2!!  Explains the algae issues quite well doesn't it?

    Now that the water quality issues were known, next up was for the purchase of the tank itself, then the sump, then the hardware.  But even before all that I began constructing my Man Made Live Rock as I was quite sure that the curing would take longer than the 3-4 weeks mentioned in the information I had read.  Thanks to the Masons for that as well as the several other "tips" they gave me.

    Ok so what's the formula?  Well without getting into to much detailed debate over strength, weight, durability, porosity, suitability for purpose, etc. etc..  The formula is 5:1  Where the 1 is one part Type 1 cement and the 5 parts is everything else you will stuff in your "Mix".

    While I read that getting cement of type "A" was the best thing you could get, do not fret if you cannot attain it.  I cannot get it locally unless I'm willing to place a large order with a commercial cement plant, and then only "wet" as they mix the chemicals in while building the mix.  I didn't want to push my luck with the union guys patience so I didn't go back to them when I couldn't find type A cement.  The local hardware stores simply do not have it in stock, nor were they inclined to order a bag or two.  At that time I didn't want a pallet full which is what they wanted for a "special order".  So back to the web I went!

    What I found out was that after reading all the information I could find it seemed that I may not want, nor really need type A cement anyway.  Seems there is, or appears to be, plenty of habitat inside regular cement for organisms of the sort we are concerned with.  Not to mention that the chemicals needed to make the bubbles may be questionable in a reef environment.

   So, the solution is as follows.  What I have done is use regular "Portland Cement" made by Quickrete , product #1124.  It comes in 94lbs., grey bags with black lettering.  These bags are under $5 dollars each!!  Hey, now that's my kind of price range.  I have used this for all of my Man Made Live Rock and it seems to be going fine.  (Time of start was fall 1999, rock looks good 3 years latter. For those interested to know.)  Just make sure the cement is fresh when you purchase it and you keep it fresh if you want to use it at a latter date.  If you use old cement your rocks will have issues.

    I understand there are many that say you should not use this kind of cement and that you need only the "White" type.  They use many reasons... "it looks better", "the coraline grows so much better on the white", "You don't want the Iron and Magnesium oxides in there"... apparently about the only reason for using the white is that the cure time is said to be considerably less. I have not used the white so cannot say for sure either way but I do know the regular works fine for me.

    There is also mention of using things such as Plastic, Noodles, Chicken feed, Cheetos, etc. in an attempt to make the rock more porous, cheaper, or more attractive to corraline. My opinion on these are well... I don't think they add anything needed that is also natural in any way, so I leave them out.  I have tried many, many things but have not found any that satisfy my standards.  If you happen to stumble across a way to make rock more naturally porous or otherwise more like the "real" thing without any side effects, be sure to let me know.

    Recently I have heard rumors of people using and recommending the addition of rock salt in their mix for porosity.  I would strongly urge anyone thinking of doing this to carefully consider the potential issues surrounding it. The first thing that pops to mind is that cement and salt are mortal enemies. With that in mind if you used it to add holes the water that the cement is using to hydrate with will have a high salt content. Salt weakens cement! While it is true that I have not done any scientific style of studies on this, it seems to me that one would not wish to weaken an already open structure by adding salt to the mix in any manner. So my opinion is to not do it.

    This rock is very porous, but not from large holes. When you pour water over the top of it it seems to suck the water up like a sponge. Or when you pull it out of water you see the water just evenly dissipate into the surface instead of pour off or through the rock.

    There are several "secrets" to getting the results that I have. One is Use water that is about the temperature you would take a hot shower in for all your mixing.  This warmer temperature helps in the formation of bubbles.  Next would be to have a spray bottle of room temperature water handy and have it set to a medium heavy mist.  Make sure you mix rather small batches at a time.  I like to keep mine under 30 lbs..  Stir like crazy to make certain you are getting enough air bubbles into the cement mixture.  If it crackles and pops similar, albeit more softly, to rice crispies in milk your doing perfect.  If not either your water is too cold, your not stirring fast enough, your ratios are way off, or combinations of these.

    So how much water are we talking here you might think.  Generally, about 1 part, but never so much as 2 parts.  This brings your total to 7 parts, but not more than 8 for a complete mix.  There are a lot of variables here, so go with feel, it should be slushy, yet firm.  Think sandcastles not mud pies. It should slide off your tools, but not flow off.  It should be wet, but not release water from it.  That is another use for the spray bottle, to add just a little more water as needed. 

   The goal is to use just enough water, but no more than needed.  Never add dry cement to a mix that is already too wet!  If your mix is too wet, it is better to start over. All is not lost however. Simply pour a rather flat rock with it paying no attention to it's shape and form. Then after it sets, break it up and use it as large aggregate in your next batch.

    After you have your mix set in your mold, you can take the spray bottle and using as few sprays as needed, clear some of the concrete grayness from the surface of the rock.  You must do this prior to burying the rock in the rest of the sand to set.  I find this works a lot better than hoping that the concrete picks up enough sand to make it look good.  An added benefit is that this exposes more clean surface area of the aragonite sand. The catch is that you can only do this to one side of the rock, so it helps to pre plan which side is up while your forming the mold. 

    After it is set and covered, I recommend being as patient as possible.  I generally wait 36-48 hrs. to make sure I get a solid rock back out of the mold.  If you do not wait at least 24 hrs. do not blame me if your rocks crumble when you remove them from the mold.  There are other reasons this can happen but taking them out to early is the number one cause.  Don't wait too long either as you do not want to run it out of available water for hydrating.  Once out of the mold I carefully place it in the trash cans of water.  I do this to ensure they have the ability to hydrate as fast as possible.

    For the molds themselves I use aquarium livestock shipping boxes.  They are quite thick Styrofoam, have tight fitting lids, and generally readily available from your LFS (Local Fish Store).  Just ask, you may just get a couple for free.  Some have deposits so be prepared to pay if needed.  The Styrofoam hold the heat in as well as the moisture.  Make sure the sand you form the molds out of is pre dampened.  It should be wet, but not soaked, and for sure not running water off of it. Try to keep the mix away from the sides as the perfectly flat side will make your rocks look perfectly un-natural.

    Some of the most natural looking rocks I have made were done by making rather large irregular thickness and shaped molds then waiting 3 days to remove them from the molds.  At that time dropping them from head high and gathering up the pieces. Wear your safety glasses when doing this!  One other thing you should do prior to making the molds is go look at as much live rock as you can.  Examine each form and shape, notice what angles are missing?  Try to make your rocks look like natural erosion took place.

    Curing is the next step and one that I found had the most conflict of available information while looking into doing this for myself.  Some said that you need 3 weeks with daily water changes, others 5 weeks with changes every two weeks, yet others said that it all depends on the volume of water that is cycled through them and how often you change the water.  Others mention using a toilets holding tank to cure rock... Sheesh!  How ya going to stick a 25lb rock in there?  Not to mention the displacement of water needed for flushing.  Some even said to give the rocks a soak in vineger...or add x number of cups to your curing vat.  Possibly vinegar is free where they come from, I do not know.  In any case I think vinegar is not a good way to cure the rock.  It could be used to speed the process I guess, but I have patience.  I'm sure it can work well for some, but I can't recommend it.

    Now most will say to monitor PH of the water in the curing vessel.  I tried that, with several different test kits.   It just about drove me nuts.  PH is an awfully dynamic specification to try to pin into a corner, it literally can change when the wind blows.  If you have an automatic PH monitor, feel free to use it.  If you don't and would rather not drive your self bonkers figuring the wild swings and often inaccurate colors of PH tests I suggest monitoring Alkalinity instead.  Or better yet, waiting the 6 week minimum then following the below method.  To be honest I don't really think one should aim for a specific "end all" specification.  Aim instead for stability first then make sure nothing is way out of whack.

    Truth is I do not even attempt any testing anymore until week 6 or so.  Then I use both Alkalinity and PH to chart any change over a two week spread.  When I get to week 6 of a curing set I take an empty salt bucket and fill it with the same water I place in the curing vessel.  Give it similar circulation and locate it in the same place so the temperature is the same.  Wait a week, then test both (at the same time) for Alk and PH.  If they test the same for PH and within one Meq/L for Alkalinity I wait another week, then repeat the test, if the test results are still the same the rock is good to go.  If they are not the same on the first or second test I start that two week testing phase over.  When they test out good they are ready.  Note that depending on what you use for your materials you may or may not have a Alkalinity difference, but if you do you should be able to get it within one Meq/L.  Also be aware that if you don't swap out the vessel to a much cleaner one at the 6 week point, you may never get good results from your testing due to the residue left in the vessel.

    I had better explain that I'm not a Chemist, so this is all my opinion based on what I have noticed happening with my own curing of Man Made Live Rock.  Tap water varies in properties from location to location.  Since it does so the reaction of the hydrating cement will also vary.  To what degree I don't know, but seems to me it would have to.  I have noticed that the "specs" I see when using RO/DI water is not the same as what I see when using straight tap water for example.  So saying that you will (or should) see specification "x" at level "y" at time "z" in your rock curing efforts seems guesswork at best.  I would imagine that there would be a predictable pattern of many water qualities in the curing stage if one was to set it up scientifically.  The issue is how close would that be to real world application for anyone who makes this type of rock?

    Some explain a condition often referred to as "Salt water Rebound".  This is where all looks well, the rock appears cured then when it is placed in saltwater it again begins to leach thus affecting tank parameters in undesirable ways.  I can't prove it (cause I'm not a Chemist) but I have the feeling this has something to do with the properties of the curing water and base materials used.  Meaning I think it is not directly relating to the act of placing the rock (and cement inside it) in the salt water but rather to the curing method and materials used instead.  That is my opinion and food for thought anyhow. 

    I messed around with a bunch of different setups. As near as I can tell it takes about 6 weeks minimum for the size, density, and porosity of rocks I make to settle down and become stable in water.  The rise and fall of alkalinity and PH seemed to have more to do with time than volume or flow of water.  Changing the water more often than every 4-7 days makes no difference that I could tell.  I also found that the volume of water was not near as important as the time between changing it.  Four days was the normal for the alkalinity and PH to build up to peak over the course of the first 6 weeks.  Changing the water before the 4 days seemed to just take a step backwards on those that I tested.  Maybe a curing vessel with a huge surface area could speed things along but I haven't looked into it.

    You also need a pretty good pump, or several pumps, that your willing to sacrifice for the cause as when your finished that pump will be all but fried out.  I use 55 gallon garbage cans to cure my rocks.  Filling the cans about three quarters full with rock consume less than one quarter the volume of water I could fit in the cans.  This seemed to confirm they were porous enough.  During the first month I change the water out every four days.  After that once a week for the second month.  I know I said about 6 weeks, and I think that would be safe, but I choose to go two more just to be safe.  At the three and six week point I drained both cans completely and cleaned them out good, the scale on them is unbelievable.  That scale is some tough stuff and gets on all surfaces.  Leaving too much of it in place seems to slow the curing process as well.  I often kill the power to the pump wait for skin to form on the top of the water then skim it off and restart the pump.  I do all this in my basement so I can only speak for myself but I would advise you to use some form of strainer so as not to plug up your drain with the silt that comes out in the water changes. Also I would recommend that you elevate the cans prior to filling them, that way you facilitate draining them with siphon.  In the warmer months I use my back deck for curing.  This makes it easy to change out the water.

    I currently just remove all rocks, wash the can, rinse the rocks, replace the rocks in the can, refill the can with tap water once a week.  I do this for at least 6 weeks before I swap the rocks to a cleaner can with a newer pump.  I then change the water every 4 days for at least 2 more weeks, then begin a 2 week testing cycle until results show they are ready for a tank.

   Several tips for a good looking stack of rocks include getting the base rocks laid out.  But I suggest that you do not try to do these first, as they are, or generally will be the largest and most difficult to make and handle.  Have the plan in mind, but do the large ones last.  My bases consist of two pieces, that have only three points of contact (each) with the sand bed.  Total surface area touching the sand is around 9 square inches.  They are high enough that water can circulate under them from any direction yet low enough to not look un-natural.

    Other advise would be to make sure you have varied shapes and sizes.  Of course you will have to plan your proportion depending on your tank size and it's footprint.  For my 75 gallon I choose to have my two bases equal to about one quarter the total, then an assortment of medium sizes equal to about half the total, then about one quarter of smaller sizes.  All but the bases are different shapes.

    Another method to get good looking shapes is to use rock that you have already made to push impressions into the sand in your molds.  Be sure not to make a bunch of identical copies however as that would look funny.

    Here is the part where you start to realize just what you have.  For example, take my base rocks.  Each is about 25 lbs.that equates to about $150 at discount LFS prices for live rock.  Do you know you can get rocks such as these from the wild that are priced like that?  I don't, yet these monsters cost me about $5 each to make, not counting my time and the cost of curing water.  My best guess is that if you could find wild rocks shaped as nice as these and are this heavy and large they would cost a small fortune.

    What you will need to do, or should do, prior to or during the making of the rock is set up a 10 gallon tank or whatever is cheapest for you.  In it you will want to start your "culture" rock. This will be used to "Seed" your man made live rock tank.  I suggest getting rather small pieces of high quality live rock that have some evidence of life.  You do not need a whole bunch, maybe a quarter of a 10 gallon tanks worth.  Of course that all depends on your ability to be patient. Some advocate using no less than 10% wild live rock too seed with.  My tank has been about 1% seeded with wild live rock.  My tank currently runs at 100% Man Made Live Rock! In my opinion what you should be looking for is variety and quality, not necessarily quantity.  Get different types of rocks that have different colors of corraline alga on them.  Try to have them not shake all the life off your seeds when you get them.  Beg if you have to as you will want every smidgeon of life there is available.  If you see select pieces that have a very small form of coral that you would like to keep in your tank latter so much the better.  Do your best to avoid rock from tanks that are over run with aiptaisia and the like.  While your waiting for your rock to cure do all that you can in order to eliminate all pests from the seed tank.  Use any methods you can come up with shy of nuking the whole thing with chemicals to ensure that your "seeds" are as clean and free of pests as you can get them.