Neptune Aquatics

Kalk, pH and the Tank.

So after Rich's unfortunate issue with Kalk I got curious about the effects some Kalk would do.

Now looking at the pH of my tank it is a bit on the low side skirting around 7.9, I used to be a bit higher than that, but... *shrug* who knows, maybe because my sump isn't on my sun porch I don't get as much fresh air transfer (plus it's much smaller). So I decided to shotgun 1/2 to 1 cup or so of saturated kalkwasser (really was guessing here due to how long I poured, I'll go for a more controlled experiment when I get some more calibration fluid to double check my probes). Tank size is 180g w/ sump it pushes it into the 200g range, surely a single cup wouldn't affect the pH that much would it?

Note: I opted for the "cheap" pH meter (i.e. not "lab grade) that has a potential error of 0.1 pH rather than 0.01 pH so keep in mind the pH could be up to 0.1 higher or lower than what the graph shows.

Now, the kalkwasser was added to one end of my overflow box, so the slow gentle flow due to the coast to coast groove allowed it to slowly progress across the 4 foot length before dropping into the sump., from there it went through the BM250 skimmer chamber, cascading into the return pump chamber, and back to the tank. So it had IMO plenty of time to disperse through the volume of water between the overflow and the pump, plus it moved extremely slowly through the overflow, now my pH probe is near the return pump so any concentrations that are in the water going into the main tank can be seen quite easily.

So what can be seen on the graph below is an immediate spike shortly after adding the kalkwasser solution into the tank, and the resolution that the controller is recording is 5 minutes too, so that spike could potentially have been quite a bit larger than the graph shows. The pH steadily rises over the next 4 hours, where I did another dose for kicks and giggles, where there was another spike.

Now it's hard to tell if the gradual climb was due to the kalkwasser, I'm guessing not since the first dose was right before the MH bulbs came on @10:30am, so that alone could cause the pH to climb as the corals (microalgae in the tank?) get more light, in fact you can see around 8am is when it starts to climb up in the first place, when my first set of T5 actinic bulbs come on. The fact the second dose doesn't have a climb like the first had me thinking "Oh pH is an exponential scale so it might not rise as much" however my MH bulbs turn off at 4pm and sure enough no more climbing at that point, with a gradual decline to midnight. This pattern can be seen with the Dec 12 pH graph which while the over all pH is higher (due to the probe not being calibrated) does in fact show the same exact pattern of a gradual rise at 10:30am when the MH bulbs come on, and a halt at 4pm to a gradual decline after they're off, although with this we don't see much of a rise due to actinic and blue plus T5 bulbs.

Initial conclusion is that Kalkwasser solution added in what might be thought as "large" amounts may not be that much of an issue to the tank, it really is a matter of relative size of "large" amount, as well as making sure that it's properly saturated before going into the tank, as what not the case with Rich's meltdown. Now it might be interesting to do a test after the lights go out so everything is "normalized" as I don't have any sort of macro algae in the system on a reverse lighting schedule, so nothing else could really affect it other than maybe temperature, but I'm guessing my results will be similar. Although it is interesting to see from a chemical point what exactly the corals are doing when they get blasted with quite a bit more light.
 
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