Re: [APD] EI dosing (Thomas Barr)

["Andrew McLeod" <thefish at theabyssalplain_freeserve.co.uk>]

> You need to add more CO2, that much I can tell you, does not matter what
> dosing you do, you'll get algae with lots of light(you would do better with
> 1/2 that amount) and poor CO2....... every time.
>
> *
>
> My tap water pH is about 8 and tank water pH is 6.5 with variations of
> 0.1unit over 24 hrs. Now as far as my knowledge goes, for a planted
> tank pH of
> 6.5 is the ideal one. If I add any more CO2 the pH will go further down and
> the whole tank will collapse.
>
> *

Here is your problem - you have a misunderstanding of how CO2 should be delivered. You do not know the CO2 content of your water.
There is no ideal pH for tanks to reach. In fact, as far as fish health in a healthy tank is concerned, pH is irrelevant; many people have pH swings of a full unit every night when they switch off the CO2. Why do you say the tank will collapse if you lower the pH any further? The change in pH due to CO2 does not affect the hardness of the water.

What you need to do is measure the KH of your water. Using a pH/KH/CO2 chart, you can then determine the amount of CO2 in your water (aim for 30ppm). For example, if your KH is 3 degrees hardness, then you want to add CO2 to reach about 6.5pH. However, if your KH is only 1 degree, you would need a pH of 6.0 (although in such a case, it is advisable to raise your KH to at least 3 degrees). If your KH was 10 degrees, then to reach 30ppm you would need only a pH of 7.0. If you tried to reach 6.5pH in such a tank, you would reach a CO2 level of about 100ppm and probably kill at least some of the fish in your tank.

These charts are always valid, regardless of any pH altering chemicals you may add. HOWEVER, there is no such thing as a KH test kit (readily available). All 'KH test kits' available for sale are actually alkalinity test kits. Provided you have not added any pH altering compounds such as 'pH Up' or 'pH Down', then alkalinity will equal KH. The use of such chemicals will therefore may this relationship untestable.

Incidentally, testing water for pH straight from the tap generally gives incorrect readings. Leave it to settle out gases overnight and come to equilibrium, and you should find that it has a pH and KH corresponding to a few ppm of CO2 (ambient levels). You then typically need to drop this level by about 1 unit (which will increase CO2 concentration by 10x). This method is not as accurate as the pH/KH method however.

Here is such a chart (ignore the color codings, aim for 30ppm).
http://www.csd.net/~cgadd/aqua/art_plant_co2chart.htm

-- 
Andrew McLeod
thefish at theabyssalplain_freeserve.co.uk

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