Manually dosing kalk (slurry method)

[Potatohead]

My tank is consuming about .1 dkh per day currently. Instead of putting kalk in my ATO, can't I just do the math by adding a few grams to say 1/10 gallon of RODI, stir, let sit for a couple hours (covered), and then pour the solution (minus the sediment) into my sump? Doing this a couple times a week seems an easier method, I can start adding it to my ATO once the tank is consuming more and I'm confident in the amount it needs. I can't imagine this tiny bit of kalk would cause a huge ph swing.

Thoughts?

 

[karimwassef]

pH swings don't really matter that much as long as you're in the 7.8 to 8.6 range.

It's the Alk swings that can hurt. If you add too much and then wait for it to drop before adding more, you could be creating a big Alk swing. If your total consumption is .1 and you're compensating with .7 a week, then you may be going from 7.3 to 8.0 when you dose that one time a week. If you do it a couple of times a week, maybe that's only like 7.5 to 7.8 and that's better.

Don't worry about pH... Keep a vigilant eye on Alk. It's the most critical reef metric IMHO.

 

[Potatohead]

pH swings don't really matter that much as long as you're in the 7.8 to 8.6 range.

It's the Alk swings that can hurt. If you add too much and then wait for it to drop before adding more, you could be creating a big Alk swing. If your total consumption is .1 and you're compensating with .7 a week, then you may be going from 7.3 to 8.0 when you dose that one time a week. If you do it a couple of times a week, maybe that's only like 7.5 to 7.8 and that's better.

Don't worry about pH... Keep a vigilant eye on Alk. It's the most critical reef metric IMHO.

Well, that's the point really, I don't want that swing. I'd rather dose it every two to three days with a tiny bit to keep it more stable. I could do that with baking soda of course but then calcium won't be in balance unless I also dose calcium chloride. The hard part is getting the dose right, it seems easier with true balling method since you can simply use the BRS calculators. Once I have been dosing the kalk successfully for a couple weeks I can do the math and add it to my ATO reservoir.

 

[karimwassef]

Just setup a very slow drip

 

[Potatohead]

Just setup a very slow drip

Yeah, thought of that and it's probably a better way to go about it... I'll do some more research. Thanks

 

[Potatohead]

Hey guys help me with my math here.

Randy Holmes-Farley says the most saturated kalk you can add at any one time, is .25% of your tank volume. This will raise ph about .1-.15 depending on CO2 levels in the tank.

So, I have a 35g system. .25% is .0875 gallons. Saturated kalk is 2 teaspoons per gallon, so this equates to .0875% of two teaspoons, or about .45% of one teaspoon. So, I can add roughly 1/25 of a teaspoon at a given time. I would likely swish in some tank water and just pour in the fluid and leave the deposits behind.

Correct?

 

[bertoni]

In a small volume of water, the Kalk probably would cause a lot of precipitation quickly. I'd just make a saturated solution. Something like 100 ml per day probably would be about what's needed. This calculator might help:

http://reef.diesyst.com/chemcalc/chemcalc.html

 

[Potatohead]

I can set up a drip but I just don't need that much right now, my frags are still smallish but alk and cal are slowly dropping. I did a water change on Sunday and they were 7.8 and 415. Last night (Thursday) they were 7.5 and 400. It's just enough consumption I don't think water changes are enough.

I was able to find a kalkwasser calculator, but it's pretty thorough and you need to know CO2 levels in the water and a few other things I simply don't know.

 

[tmz]

The pH isn't the only worry;slurry adds impurities and likely some undissolved calcium hydroxide. Alk swings are also likely likely and can be devastating to some corals.

 

[Potatohead]

I think I'm going to have to get some calcium chloride and just manually dose two part until I get the kalk dialed in the top off. I already have baking soda and mag chloride and mag sulfate here. I can start out really low like one teaspoon per five gallons and see where that keeps the tank and supplement two part until the next top off batch is needed, and I can adjust then. Doing the math if I wanted to drip it I would have to only drip one drop per 6-7 seconds which just seems too slow to be consistent and reliable. I can't use less kalk and drip more because I don't evaporate that much.

 

[tmz]

That would be fine. However kalk can easily be dosed slowly and evenly over the course of 24 hours independent of an ato via a still reservoir and peristaltic pump.

 

[blasterman789]

pH swings don't really matter that much as long as you're in the 7.8 to 8.6 range.

Let's ask a dead coral reef in the Pacific what it thinks about that. Nah, nothing wrong with 7.8 at all.

pH swings are likely the biggest cause of poor SPS growth in modern reef tanks. There's a reason a 400 gallon tank handles this better than a 10 gallon.

 

[bertoni]

Acidification via carbon dioxide definitely can cause bleaching and coral death. Google turns up a number of studies on the subject. That said, 7.8 looks like it's tolerated reasonably well by a number of species, and we can increase the alkalinity of our tanks to compensate, as well. A lot of very nice tanks have run at 7.8. Those tanks might show more growth at higher pH levels, but keeping a reef indoors requires tradeoffs for most of us.

 

[tmz]

While I prefer constancy in pH above 7.8.(8.15 to 8.35 diurnal swing in my system ) for a number of reasons ;many do fine at 7.8 to 8.5. Dirunal swings are common on natural reefs;so I'd consider a swing of 0.2pH inconsequential as long as the bottom was above 7.8. (Calcium carbonate including coral skeletal mass can begin to dissolve at 7.7)

I consider alk constancy much more important than swings in pH much with alk swings more harmful particulary to sps . Hence using buffers to bump pH is a false trail leading to alk changes with little to no long term pH effect. Controlling CO2 content in the water is achievable without bumping the alk around via:

more fresh air in the room :

an airline with outside air to the skimmer intake ;

kalk in lieu of some or all two part dosing or calcium reactor dosing;

more photosynthesis via algae refugia or more photosynthetic organisms in the tank (swings can be reduced with opposite photo period routines);

a CO2 scrubber.