Let's say I dose 200ml of kalk every 2 hours. First case dose 200ml kalk in 5 min, second case stretch out the dose to the whole 2 hours. Assuming a same starting pH, will the end pH in 2 hours be the same for both case?
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Yeah, I think so because it will consuming the same amount of CO2. I like the slow as possible approach though.Let's say I dose 200ml of kalk every 2 hours. First case dose 200ml kalk in 5 min, second case stretch out the dose to the whole 2 hours. Assuming a same starting pH, will the end pH in 2 hours be the same for both case?
As folks have noted, adding hydroxide in any form (such as kalkwasser or my DIY two part ultra high pH recipe) consumes a fixed amount of CO2 per unit of alkalinity added, regardless of timing.
BUT, as soon as the tank is placed at a deficit of CO2 relative to the air, the tank begins to pull in CO2. If you dump a bunch of hydroxide, the pH jumps up and then falls back as the tank slowly pulls in more CO2. That might take hours, but not days.
IF you slowly spread out the same hydroxide addition, the jump is proportionally smaller each time, and the CO2 addition from the air is also spread out.
If you add it slowly enough (24/7 drip, for example), the tank will just average a slightly higher pH and you will not ever see a rise or fall back.
Which has the highest average pH over 24 h? I suspect it is the slow addition, but have not actually tried to measure it.
So when dosing fast and have higher pH spike, the CO2 in the tank is lower than slow dosing. Tthe CO2 difference between the air is higher, thus the osmotic pressure higher, and lead to CO2 pulling back to the water faster? I most interested in how much the difference there would be.
For the reason of the question, I'm currently dosing kalk using the Kamoer X1 pump. It's set speed at 40ish ml/min. So I want to get an idea how much of an improvement it would be to smooth out the dose can bring, and if it justify the cost of it. The spike is about 0.03, so can I assume the improvement will be less than that? More like 0.01 improvement in average pH as an optimist guess?
Yes, although it is not "osmotic" pressure. It is concentration of CO2 in the water and the partial pressure of CO2 in the air.
The immediate pH spike is about 0.6-0.7 pH units for each 1.4 dKH added instantly to seawater. I'm not sure what you mean by the 0.03 pH units, unless that is from a very small addition.