[APD] Re: RO/DI setup vs. CO2 setup

["Tom Wood" <tomwood2 at flash_net>]

"The area where I live in St. Louis, MO has very hard water (high 
GH) also the pH tends to run around 8.0."

Hard water is not necessarily a bad thing for most plants. Test 
the pH several hours after it has been out of the tap. Many 
municipal water systems drive CO2 out of the water to make it 
less corrosive to the pipe system. Once out of the tap, the water 
will take on CO2 from the atmosphere and reach its normal pH. 
Ours comes out of the tap around 9 and drops to 7.6 all by 
itself.

"I have adjusted the pH down to neutral, with SeaChem Discus 
Buffer."

Discus Buffer is monosodium phosphate. Depending on how much you 
added, your phosphate level is now likely measured in the 
hundreds of ppm, when the desired level is 1-2 ppm. Keep the 
Discus Buffer for dosing phosphate later but don't use it for pH 
control. Flush the tank and start over.

"But, the water is so hard that I have been able to get an 
accurate reading with my test kit. The vial fills up before the 
endpoint is reached."

Which test kit for what parameter? You'll enjoy the tank longer 
if you don't fight your tapwater. So in the end, the actual value 
doesn't really matter.

"1) Does a test kit go "bad?""

They can, but 'user error' plays a role too.  :-)

2) Would a RO/DI filter be a better purchase for the long-run 
than a CO2 setup?

No, buy the CO2 setup and don't worry at first about hardness. If 
you get into exotic plants/fish that -really- need soft water, 
then consider RO. Most 'soft water' plants/fish do fine in 'hard' 
water. Measure KH, buffer to about 3 using baking soda if needed, 
and then add CO2 to get to about 20 ppm using the charts:

http://www.thekrib.com/Plants/CO2/kh-ph-co2-chart.html

You'll see that adding CO2 will also bring the pH down, but 
that's an effect not a goal.

In My Opinion, others will chime in.

TW 


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