Re: Laterite Question

["Jamie Johnson" <jjohnson@davisfloyd.com>]

Matt wondered:
> I recently moved & reset up a 30 gal. tank.  Over the past 2 months,
> the PH in the tank has drifted upward as has the hardness.  I live 
> in NYC where the tap water is neutral and fairly soft.
> Before the move, the hardness was routinely 70 to 70 ppm.  
> Now it is more like 110ppm.  The PH is about 7.2-7.4 although it is hard 
> to tell with my cheap test kit  

>As I understand it, laterite has lots of iron, but it should not be 
>soluable & should not affect the PH.

Well, Matt, yes and no. I really can't speculate what caused your 
changes, but I would bet the laterite is the culprit. I'll give you 4 
different ones I studied: (pH measured with equal amounts of DI 
water and laterite, Orion meter)

Substrate Gold - pH = 4.9, soft, will disintergrate when disturbed, 
causing all kinds of mess. 4-5% Fe.

First Layer Pure Laterite - pH = 5.7, medium hard to soft, will cloud 
water when disturbed. 11-13% Fe.

Dupralit G - pH = 6.3, soft, will disintergrate. 8-10% Fe.

And now the kicker: CaribeSea Laterite - pH = 9.8 ( yes, that's 
right!) hard as a brick, will not cloud water once rinsed, no rxn 
when treated with HCl, so no CaCO3/MgCO3 to drive the pH up. 
Actually had the same amount of Ca as the previous three. 0.4-1% 
Fe.


As you can see there's all types of laterites out there. (That's why I 
did the study) So, if the efforts of keeping a soft, acidic 
environment, I would go with something a little more inert, i.e. 
Flourite, Turface, or another calcined clay product. The laterites are 
good for plants, but so are the calcined clays and they play lots 
less havoc on your water parameters. In a planted tank the 
increase in pH and hardness would probably be negligable, but for 
breeding apistos it may have an adverse affect (if at all). 

Jamie    <"\\\><


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