Day and Night testing ?

[comatose]

Other than PH does any other testing kits make a difference whether you test before or after lights out ?

[Randy Holmes-Farley]

No,I don't think that anything else changes much day to night. So you can just test whenever it is most convenient. :)

[Bojan]

I found out that Alkalinty (KH) is higher in the morning for 0,14 (0,4KH) than in the evening. That is acctually not very important, because difference is very small, but on the other hand it is interesting.

Alkalinty dosing in my tank is constant, because I use Ca reactor, so I suppose that this is why corals not use alkalinty during night time. Randy please correct me , if I am wrong.

[Habib]

There are two (and perhaps more) effects on KH measurement vs time of the day. However, they are usually very small.

One is the pH effect. A lower pH due to CO2 will give a slightly lower reading due to a higher conversion of borate to boric acid.

The other one is feeding. Several organics will consume some acidity and can result in a higher alk value.

[Bojan]

Originally posted by Habib
A lower pH due to CO2 will give a slightly lower reading due to a higher conversion of borate to boric acid.T

In my tank Ph in the morning is 0,4 lower than Ph in the evening, but alkalinity is 0,4 KH higher in the morning than in the evening.

Originally posted by Habib
The other one is feeding. Several organics will consume some acidity and can result in a higher alk value

It is possible that this explain my case, if this process is more active during the night time.

[Randy Holmes-Farley]

Alkalinty dosing in my tank is constant, because I use Ca reactor, so I suppose that this is why corals not use alkalinty during night time. Randy please correct me , if I am wrong.

The CaCO3/CO2 reactor will also be more effective as the pH in the input water declines. So I would not assume that the output is necessarily constant. :)

OTOH, calcification by corals and other orgaisms may also not be constant day to night, possibly causing small changes in alkalinity.

[Bojan]

Originally posted by Randy Holmes-Farley
The CaCO3/CO2 reactor will also be more effective as the pH in the input water declines. So I would not assume that the output is necessarily constant. :)

I didnt mentioned in the previous post, but i measured PH in reactor and output (KH,Ca) of Ca reactor in the morning and in the evening many days with constant flow and bubble rate and i found out that Ph and output are quite constant. I agree, that Ph inside of reactor depends on the Ph of the tank, but ....

If pH in tah tank drop for 0,4 , Ph in the Ca reactor will drop for less than 0,05. I suppose this is why, Ph is in the logaritmic relation with CO2.

In any case I also measured KH and Ca production in the morning and in the evening and I didnt find any difference. It is possible that there is a little difference , but i can not measure such small diffrence. I used Salifert KH, Ca tests and electonic PH meter.

KH consumption in my tank is aproximatelly 25 KH liters per hour, what means in 400 liter tank 0.06 KH reduced alkalinity per hour if Ca reactor is stoped. Based on this data it is possible to calculate, that Ca production have to be significantlly changed (more tan 50%) to result in 0,4 KH morning, evening swing.


Originally posted by Randy Holmes-Farley
OTOH, calcification by corals and other orgaisms may also not be constant day to night, possibly causing small changes in alkalinity.


That seems very logical to me.