# Stupidly used oyster shell gravel...



## Tom (22 Aug 2010)

I've just realised why my pH has been a bit high. I used some nice 1-2mm light coloured gravel that I had lying around for my latest nano, thinking that it was just an inert gravel. It looked nothing like normal coral sand as it was very smooth, and the Unipac bags don't seem to have any names on the bags as far as I can see. Thing is, it turns out it's Oyster Shell sand, and my pH has shot to 8. Does this mean I will have trouble getting enough carbon in the tank? I seem to remember, as the pH goes up, it's harder to get enough CO2 in. Or maybe I'm making that up!

 Is it do-able with this high pH using Excel, or am I best to swap out the gravel? (will be a right pain, as I've just planted it!!!)

Cheers
Tom


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## Tom (22 Aug 2010)

I have just ordered some Branco sand from TGM which has worked out ridiculously expensive on postage, so not happy about that. AquaEssentials seem to do the same weight for almost half the price. 

Would still be interested to know more about the sand I have currently now though 

Tom


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## ceg4048 (23 Aug 2010)

Tom said:
			
		

> ... it turns out it's Oyster Shell sand, and my pH has shot to 8. Does this mean I will have trouble getting enough carbon in the tank? I seem to remember, as the pH goes up, it's harder to get enough CO2 in. Or maybe I'm making that up!


Hi mate, long time no see.   

The Matrix made that up, then broadcast the faulty data across the neural network for download to your brain. Alkalinity has only a very minor effect on CO2 solubility. Nothing to worry about mate. 8) 

Cheers,


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## Tom (23 Aug 2010)

Yes it has been a while, but I think I'm back for the time being   

OK then, no wonder I couldn't find much info!!    Well I've bought that ADA sand anyway so I'll just swap out the visible parts and leave the stems in place at the back rather than disturb the whole layout. 

Obviously this tank may still have a high Alkalinity and GH, so will this bother or hinder the plants at all? My last setup hovered around 6.4 with rainwater and Aquasoil. 

To quote from an ADA Aquajournal water quality article:
http://www.aquajournal.net/na/water/plants_prefer.html

_"The form of carbon dioxide depending on pH When the pH is low, CO2 is present in the water as free carbon dioxide (CO2). There are more bicarbonate ions when the water pH is near neutral. When the water has a high pH, carbonate ion (CO3-) dominates."_

The accompanying graph shows that at around pH 8, CO2 and CO3 are at their lowest, whereas HCO3 is at it's highest. Would there be any noticable difference in plant uptake and usability through each? He also says, different plants prefer carbon in the different forms, so presumably there is a happy medium at around 6-7 where CO2 and HCO3 are equally present?

[EDIT: just tested my KH/Alkalinity - it's at 15]

Cheers,
Tom


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## ceg4048 (23 Aug 2010)

Yeah, the explanation in the article is completely bogus unfortunately. They have misinterpreted the chart. The confusion arises mainly because the data describes the shift in equilibrium that occurs only with the portion of CO2 that converts to Carbonic acid. But only a very small percentage of the dissolved gas actually forms carbonic acid, and this is the portion that reacts in the equilibrium equation with carbonates and bicarbonates. This explains why the dropchecker colors for example do not change very much when high carbonate content water is placed in the checker, yet the colors changes wildly if soft water is used. The carbonate/bicarbonate content acts as a buffer against the effects of the carbonic acid. This is exactly why it's no good using anything other than a known KH value distilled water in the dropchecker.

So people put high KH water in their dropchecker and add CO2. Then the dropchecker color stays blue because the carbonates absorb the carbonic acid. So, they conclude it's because CO2 is not dissolved in the water, which of course is an illusion.

KH has nothing to do with the solubility of the gas in water. Depending on temperature, only about 0.1% to 0.2% of the dissolved gas converts to Carbonic acid, so that chart you see and that explanation you're reading only applies to 0.1% to 0.2% of the CO2 in the water. The other 99.8% to 99.9% of the dissolved CO2 is unaffected by this chart.

This is so blatant. See how they cleverly weave into the fabric of their text references to their products to suck you in?





> Pearl Grass prefers a little higher pH and hardness because it uses injected CO2 in the form of a bicarbonate ion (HCO3-). An addition of Brighty K, which has a pH buffering effect, is effective for preventing pH from decreasing too much.


Oh sure, just go and spend your money on our Potassium product and that will cure a problem you don't even have. 

Good grief, what propaganda! Let's take a break and have a munch on a reality biscuit. Here's a tank with KH over 15 and water parameters completely opposite to what the journal tries to make you believe is optimal:






The Matrix isn't real Tom!

Cheers,


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## Tom (23 Aug 2010)

And I thought I could trust an AquaJournal!!   They're no different to most businesses really I suppose - they need to make money on anything and everything they can! My lecturer at Sparsholt was right when he said Bull**** Baffles Brains!   

Cheers again for another good explanation  I'll be happy with my pH 8 then   

Tom


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## ceg4048 (23 Aug 2010)

Well, you can trust them for Aquascaping advice. No doubt about that mate.  

Cheers,


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## Tom (23 Aug 2010)

> Well, you can trust them for Aquascaping advice. No doubt about that mate.



This is true


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## LondonDragon (25 Aug 2010)

With that kind of PH it would be ideal to keep some Sulawesi shrimp in there


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