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Discussion Starter · #1 ·
So I have had a 10 gallon tank and some drift wood sitting around for about a year now and I finally decided to do something with it! I want to build a rock wall, so with the help of reading some other construction threads (mainly the ones suggested here: http://www.dendroboard.com/forum/parts-construction/44960-can-somone-explain-fake-rock-bulding.html ) I went and bought some supplies today.

Here is what I'm starting with:

10 gallon tank, cement mix, a bucket for mixing, non-toxic acryllic paint in black and white, paint brushes, painters' tape, great stuff, driftwood, hot glue gun, glue, razor blade, scissors and polyethylene foam.

I couldn't find the specific types of concrete used in other posts. Home Depot had some grout and large bags of concrete. Lowe's had a little bit more selection and this is what I came up with. The only "underlayment" cement I saw came in a huge bag so I didn't get it. Hopefully this one will work:


I also want to point out the painters' tape I got... FROG tape! I had to buy it just for the name:)


So now I am trying to decide placement of things... I really want to use this driftwood I have, but it takes up a lot of space. Also not sure how to work it in with the "rocks." Suggestions welcome!
 

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Discussion Starter · #2 ·
My first step was to use Great Stuff to "glue" the driftwood in place:


Next I hot-glued all of the "rocks" into place:


Then covered as much of the driftwood as I could with painter's tape and poured a thin layer of concrete over the foam and worked it in with my fingers:


After this step disaster struck.... I thought my next step was to fill the tank with water to cure the concrete. This seemed to dissolve the concrete that was on the rocks, fill the foam up with water, made the foam float off the glass (not enough hot glue I guess) and painters tape come off the driftwood.... I'm going to let everything dry out and then repair... going for the misting method of curing next time instead of tub.
 

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After the cement, or concrete is put on your background all you need to do is let it cure. You do not need to fill with water or mist to make it cure, it will cure on its own. Spraying water on concrete to strengthen it is usually only done on garage floors or driveways because curing with water makes it stronger than curing with air. For your situation you def do not need water to help cure.

Just so you have a better understanding of how Quikrete concrete works.....
1. You mix powder with water to get desired consistancy.
2. You apply to desired surface.
3. You let cure 24 hours or so........with air contact vs. water contact.

And the industrial, residential or commercial concretes that use water to cure....
1. Concrete truck mixes heavier duty concrete in truck.
2. Concrete truck pours into desired area.
3. You work concrete to desired finish.
4. Concrete begins 28 day curing process, which involves spraying down your garage floor or driveway with garden hose, once or twice a day for those 28 days.

( I have never heard of a concrete that is submerged in water to cure, this will simply dilute the mixture making a very weak cured product, or will wash concrete off of desired surface entirely. )

What you had so far looked good! Don't get discouraged, trial and error is the best way to learn! Good luck on the second try! :D
 

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Use Aquarium silicone glue to attach the foam to your tank.
use a spray bottle to keep the concrete a bit moist.

Take TIME to to build that rock wall!
 

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Discussion Starter · #5 ·
Thanks for the advice and encouragement! I know NOTHING about concrete so it was helpful to have an explanation.

After letting everything dry out I re-glued on the background:


Then did my thin layer of concrete:


I let that dry for about 2-3 days and put my second layer on today:


Having never touched concrete before I was surprised how much I could shape it. I was definitely overly concerned about the shape and placement of the foam before the concrete went on!
 

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Discussion Starter · #7 ·
Looks good. Don't forget about the vinegar neutralization step, it is very important.
Yep I've got a bottle of vinegar and a pH test kit, so I will make sure it is neutralized before anything living goes in. Thanks!!
 

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Discussion Starter · #8 ·
Took the painters' tape off today and cleaned up the sides with a razor:


Then checked the "run-off" pH by misting the rocks:


definitely not neutral... spritzed with vinegar and will check again soon.

How does the shape of everything look? Should I do anything else before painting??
 

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Discussion Starter · #9 ·
okay, so how long does the neutralization usually take?? I have spritzed with vinegar several times over the past 2-3 days and every time I test it's still basic. I'm getting impatient! Maybe I can try H2SO4? :)
 

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okay, so how long does the neutralization usually take?? I have spritzed with vinegar several times over the past 2-3 days and every time I test it's still basic. I'm getting impatient! Maybe I can try H2SO4? :)
It can take weeks.
I've seen some submerge the rack wall in vinegar water and I've seen some just spray.
It takes a long time for the pH to neautralize.
You gotta have patience
 

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I am a little confused, but no worries this seems to happen a lot.

One person said you need to do nothing to let it cure, but others have said you need to keep it moist with water. Now, you are spraying it with vinegar to help neutralize???:confused:

To spray or not to spray.............that is the question.
 

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Discussion Starter · #12 ·
Some threads I read said to keep the concrete moist while curing, others said to soak it, others said just leave it.

The vinegar has nothing to do with the curing- trying to get the pH down due to alkalinity of the concrete.

On another note... out of curiosity I used my pH test kit on the water out of the tap at my house-- same bright blue color that is showing when I test the concrete! Then I tested water out of my Brita pitcher (same tap water, just filtered) and the test came up bright yellow. Now 6 semesters of chemistry that I took in college should help me to figure this out, but I am confused. Is the pH of tap water that variable? And do I need to get a test kit that doesn't have such a narrow range?
 

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you could always try testing the tap water and then put the water you tested into the brita pitcher and test it after it has been filtered and see if it comes back yellow. This would tell you the tap water isn't variable in it's acid/base, but is being changed through the filter.
 

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Discussion Starter · #14 ·
So seeing as my tap water is slightly basic and my filtered water is slightly acidic... I decided to test the run-off of the rocks using the filtered water since my tap water would give me a basic result no matter what. Run off was acidic this time. I am assuming the rocks are neutralized and that I am only testing the pH of the water that I'm putting on them. I have used an entire bottle of vinegar and rinsed them with copious amounts of water several times, so I think they will be safe. I think next time I would opt for a pH test kit with a broader range.
 

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people say to soak or spray the cement in order to help it cure and set without cracking. Once it is fully cured, people will then soak it in vinegar to counter the high ph quicker. the concrete ph will settle over time regardless of the curing style.
 

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It can take a couple of weeks at least to cure, at least, with daily saturation. Then you really have to use a lot of vinegar to nuetralize it. It has to be saturated with vineagr many times, allowing it to dry and then saturating it again. It is the most annoying and tedious step but the most important of all. Well worth taking the steps in the long run.
 
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