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PostPosted: Sep 18th, '16, 00:30 
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Sounds like one of the two or both of them had some calcium carbonate. I had some of this with the red volcanic rock (aka red scoria). It took a couple of years for the pH to come down without doing any pH adjustments. Try them out with a few drops of vinegar and see if they fizz. I had some white areas on the scoria that did but most of it didn't.


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PostPosted: Sep 18th, '16, 05:06 
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I did notice some white stuff. Will that small an increase of pH make a difference?


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PostPosted: Sep 18th, '16, 07:36 
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pH in my teeny test system was around that when I started out (with scoria/red lava rocks and expanded clay), and kept nudging back up when I tried to adjust it down, but then abruptly dropped to 7-7.5 and stayed there. My big system has the same media, but started out at 7-7.5 and hasn't varied much from that... possibly because I'm washing all the scoria really well. I'm guessing the dust in the first batch had something in it that was buffering things up.

(I'd probably be done building already if I wasn't washing the scoria, 'cause I can't manage it unless I'm in tip-top shape and preferably have my husband helping :-P )

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PostPosted: Sep 18th, '16, 08:09 
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chris81 wrote:
Will that small an increase of pH make a difference?


Yes and no. It may look like a small change but the pH scale is logarithmic and based on 10 so a change from pH 7 to 8 represents a 10 fold change and if the solution then went from 8 to 9 it would be 100 times more basic than it was at pH 7.

In this case it might not change how you treat the system since you're probably already planning to use Iron (sprayed on) or chelated iron (either sprayed on or added to the system water).


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PostPosted: Sep 18th, '16, 08:21 
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I was considering Rusty metal now before I needed to add it.


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PostPosted: Sep 18th, '16, 09:50 
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pH is now 8.4


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PostPosted: Sep 18th, '16, 10:02 
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Rusty metal won't help, it won't be available to the plants because of the pH - you'll need some EDDHA iron chelate or you'll need to spray apply something like maxicrop plus iron. Spray applying the iron avoids the pH lockout you'd get if you added it to the system water.


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PostPosted: Sep 19th, '16, 00:16 
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Is AP like soil in the sense of when you grow and take away the fruit or veg that it takes away from soil and brings PH down?


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PostPosted: Sep 19th, '16, 02:27 
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No matter how you grow something when you remove it you remove the nutrients that built it. I'm not sure where the idea of removing the fruit lowers the pH comes from, I haven't heard it. I suppose removing fruit might cause the plant to draw up other nutrients to form another fruit or something along those lines but the nutrients in that first fruit are already out of the soil by the time you pick it and should no longer affect the pH. The pH lowering in AP is usually coming from nitrification but in this case it's likely that carbonates buffer the pH up. When you've used enough of the carbonates up then the pH will come back down but depending on how many there are it could take years or it may only take a few weeks :dontknow: .


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PostPosted: Sep 19th, '16, 05:14 
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so basicly rock cleaning tomorrow, bummer. I only filled one GB though so not to bad. 26 cubic ft of rock.


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PostPosted: Sep 19th, '16, 07:21 
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Try the vinegar test on some of the scoria you have and see if it fizzes indicating that carbonates are present. If you're only getting fizzes from rocks that have white portions then take those out.


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PostPosted: Sep 19th, '16, 08:27 
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ok. thanks scotty


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PostPosted: Sep 20th, '16, 03:35 
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Dumb question, if certain rocks can increase ph, is there an equal opposite? to keep from picking thru so much rock, is there another type of rock to add that will balance the ph?


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PostPosted: Sep 20th, '16, 05:30 
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No equal opposite that I know of but some would lower the pH - it is unlikely you'd get the amounts of base and acid in the rocks to balance out. It would be a lot more work to even try this than it's probably worth. Most people wait for the pH to come down due to nitrification but in some cases it's possible to adjust with Hydrochloric aka muriatic acid. This should be done gradually by adjusting the top up water to a pH of 6.5 and then gradually adding this to the system - the idea is not to shock the fish/plants/bacteria with a rapid pH change.

You can figure out if pH adjustment will work by trying to adjust the pH on a know amount of system water and rock. Keep track of how much acid it takes to adjust the sample pH to 6.5, just keep letting it sit and then adjusting until it's finally stable (you may need to let it sit overnight a few times). Keep a running tally of the amount of acid you used. You can figure the rough amount of acid you'll need for the entire system by plugging in to this formula -

Amount of acid needed for system = system volume X (amount of acid needed for sample/sample volume)

a 5 gallon bucket is probably about right for sample size - too small and it won't be as accurate.


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PostPosted: Sep 20th, '16, 07:30 
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ok, just picked thru the rock. filled with water, let it settle and ph is 7.4 will test again in a few hours and then circulate and test.


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