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hello all,

*** been reading some about DIY background and it is told that a couple of water changes is neccessary in order to get the same PH in the tank as the tap water.

What is the deal with this? Why would water changes lower the PH and not a good 1h rinse of the background outside the tank with a regular hose?

confused

regards,

vacholino
 

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As an example, I just made some "custom" rocks out of cement. I've been soaking and "curing" them in tubs of water for about two weeks now, and the pH is still elevated.

It's gradually dropping from "totally off the charts" to now something around 8.4 or 8.6 after soaking for 24 hours.

You're typically not talking about soaking for a few days; you're talking curing it for two full weeks or more.
 

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Would it work to let the concrete cure for a full 30 days before submerging it? By then the cure should be complete and there should be nothing left to leach out. I would think that the only thing you would need to do is rinse off the outside. Just a thought.
 

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Stickzula said:
Would it work to let the concrete cure for a full 30 days before submerging it? By then the cure should be complete and there should be nothing left to leach out. I would think that the only thing you would need to do is rinse off the outside. Just a thought.
As water will soak a little into the concrete you'll get some leaching after all. Also the concrete will cure better if kept wet.
 

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Stickzula said:
Would it work to let the concrete cure for a full 30 days before submerging it? By then the cure should be complete and there should be nothing left to leach out.
Any concrete will continue to harden for 99 years before it is fully "cured" on a molecular level. The longer you can wait to submerge it the less it will leach and the less water changes you will have to do.
 

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My hunch, though, is that the fastest method is still soaking your work in water.

Sure, cement cures in air, but you're supposed to be "spritzing" it with water to keep the material damp. Cement needs moisture to cure.

Assuming time is of the essense, just soak in water and change it daily or every other day. Or, leave your work outside and let nature keep it periodically moist, but I suspect it will take longer ultimately.

After two weeks, I'm starting to see my pieces drop off in the amount of alkali substances they are releasing.
 

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So spritz it for a couple weeks adn then soak it for a couple weeks at least?

About 1 month from day the concrete is applied until its safe for fish?
 

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Eb0la11 said:
So spritz it for a couple weeks adn then soak it for a couple weeks at least?

About 1 month from day the concrete is applied until its safe for fish?
I would do one or the other. Either submerge and do water changes or leave it outside.

If I were to do it outside, I would put a damp towel over it and cover it with a tarp. Then I would check it every few days until the towel is dry. Then re-wet the towel and repeat the process. The purpose of keeping the surface damp is to ensure that all of the concrete cures properly. If the surface dries and the concrete beneith it is not cured, the first layer will flake off. Spritzing everyday is more work than laying a towel over it and forgetting it for a frw days.

If I were to soak it, I would put it in a large trash can outside. Place the can near a drainage area on your property. This could be where your driveway drains into the street or somehwere that rain water colects, but definately somehwere that can handle lots of water. Then run your garden hase into the can securing it somehow. Use a ball valve at the end of the hose to control water flow. Set it so that it will overflow very slowly, maybe like 20g/day???. Then after a day or 2 check and note the pH. Do check and note it as often as you like, but I would probably only do it once a day for the 1st week then once a week or so after that. Hopefully the continual flow of fresh water will help it cure faster by providing more free ions for the chemical that leeches out of the concrete to attach to. Plus the continual overflow will prevent the need for manual water changes. Please note that the 20g/day is just a guess. I have no idea of the actual amount of overflow that would work best. If the pH is NOT continually very high for the 1st week, then I would decrease the flow, but if it is off the chart after the first week I would increase the flow. I don't know for sure if the continual flow will decrease cure time, but it seems like it would.

If I had the time, I would do the outside cure. Saves water!

I have also heard of people adding lots of salt to the water to help create more free ions and thereby decreasing the cure time. Some people say it works and some don't.
 

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I opted for the soak in a tub approach.

I agree with previous poster -- use one approach or the other. I waited only two days before sumberging mine... just long enough to make sure the cement hardened to the point where nothing would break off.
 

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Stickzula said:
Would it work to let the concrete cure for a full 30 days before submerging it? By then the cure should be complete and there should be nothing left to leach out. I would think that the only thing you would need to do is rinse off the outside. Just a thought.
That makes perfect sense, since you have all the concrete research ever done and experiences of professionals backing you up. However hobbyists are impatient, sure they can find a shortcut, and sure the rules must be different for them since "after all they are not making a sidewalk". Most of the curing will be done after the 30 days of misting or loosely wrapping it in plastic, however the curing of concrete keeps going on, ever more slowly. There probably is no reason to do water changes, or to drop the rocks into a running stream from a hose. You are not really leaching out alkalies in significant amounts, you are creating a biological film that seals the rock from the water, the same biological film that processes ammonia and nitrogenous wastes from fish in a biological filter. It takes about two weeks for the "cycle", and no surprise, the same amount of time for the rock to "leach" out.

My method is to set the rocks, driftwood base, cave, or background into a large container, fill it with water and some oak leaves, add several Gambusia since they tolerate high pH, the nitrogen cycle, temperature swings, and as a plus they devour mosquito larvae if you do this outside. If it rains, there is a "water change". If not, there isn't.

And PS, there are some shortcuts. It's just they are not as cheap as Portland cement, and require techniques that are harder tro learn, and less forgiving of mistakes.
 

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gherlevi said:
My hunch, though, is that the fastest method is still soaking your work in water.

Sure, cement cures in air, but you're supposed to be "spritzing" it with water to keep the material damp. Cement needs moisture to cure.

Assuming time is of the essense, just soak in water and change it daily or every other day. Or, leave your work outside and let nature keep it periodically moist, but I suspect it will take longer ultimately.

After two weeks, I'm starting to see my pieces drop off in the amount of alkali substances they are releasing.
Cement needs moisture to cure, but also it needs air, so submerging it will greatly slow the cure rate unless you have used a hydraulic cement (one that comes with its own oxygen source in the formula). I could use the same hunch above to incorrectly guess that the best performance from a wet/dry would be if I submerged the whole thing. In both cases it's the combination of air and water, not one or the other that works best and fastest.
 

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Mcdaphnia...

Thanks for the tip. I didn't know if exposure to air was necessary or not.

I've been basically following the recommendations found here:
http://www.reefs.org/library/talklog/t_ ... 52498.html

From what I read, it seemed that most shortcuts lead to suspect results, and just soaking the stuff in water and waiting patiently was the best bet.

Are you suggesting that a cycling of soak, dry, soak, dry would be best?
 

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NOt trying to speak for McDaph, but I think the suggestion is continuous exposure to moisture an air simultaneoulsy is the fastest...

i.e. optimal might be the "wrap in damp towel" which I saw on mythbusters, so it must be the best way to do it :)

Or, perhaps continously misted with a fine spray, but I don't think it;s worth making a rig to do that :)
 

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gherlevi said:
....Are you suggesting that a cycling of soak, dry, soak, dry would be best?
You cure your rock best with both at the same time if you follow me. Enough water to keep a "light sweat" on the surface of the concrete, but not enough for there to be dry areas or inundated areas. Concrete is made by reducing limestone to a chemical that has had the chemically linked water and oxygen in limestone forced out. Adding water kindles a reaction similar to combustion. Instead of oxygen, fuel, and heat, you need oxygen, anhydrous lime, and water. What you end up is a limestone matrix encasing whatever aggregates you mixed in, sand, perlite, etc.

When I was a little kid, my labor was cheap enough (work for Coca-Cola, candy bars, and bologna sandwiches) that my dad would leave me at a construction site with a squirt bottle and a bucket of water. Now they have chemicals that block evaporation and work even cheaper than I did, but I choose not to use them on aquarium stuff.
 
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