Dosing Kalkwasser into a pico tank

Myka · Mar 20, 2018

Sorry, I don't know the math to figure this out myself, could someone please post the math so I can do it myself next time?

I'm considering adding kalk to my pico. It does not have an ATO (too bulky), so I'd like to know if this looks like a good idea or a bad idea on paper before I try it out.

The display itself is 10 liters (2.6 gallons), and has a total net water volume of 13.8 liters (3.6 gallons).

Right now I'm adding 100-200 mL RO/DI water for top off per day, split into morning and evening additions. The pH is low, and sits around 7.6 - 7.7 pH units.

How much saturated kalkwasser can I add to the pico before I am causing too great of a pH swing? That, I will probably have to experiment with, so maybe a better question would be, how much pH swing will I get from adding 50-100 mL manual doses of kalkwasser at a time? In 12 hours, will the pH go back to what it was before the addition, or will I get a cumulative effect?

Thanks for any help!

Midrats · Mar 20, 2018

Check the reef chemistry calculator.

chipmunkofdoom2 · Mar 20, 2018

Per Randy, adding 1.25% of the tank's volume of fully-saturated kalkwasser will raise the pH by 0.7 pH units. So adding 200mL (which is about 2.6% of your tank's total volume) would raise your pH by 1.4. It's worth noting, however, that the effect will be relatively short-lived.

Is your pico open or sealed to reduce evaporation? It sounds like it's not getting very good gas exchange.

Randy Holmes-Farley · Mar 20, 2018

100 mL of saturated limewater added to 10 liters of reef aquarium water will likely instantly boost pH in the whole tank by about 0.5 pH units. It will also boost alk by 1.15 dKH. That's too much at once for either pH or alk, IMO.

Myka · Mar 20, 2018

squareriggersailor said:
Check the reef chemistry calculator.

The calculator give values for Ca and KH, but it doesn't actually give pH values.

chipmunkofdoom2 said:
Per Randy, adding 1.25% of the tank's volume of fully-saturated kalkwasser will raise the pH by 0.7 pH units. So adding 200mL (which is about 2.6% of your tank's total volume) would raise your pH by 1.4. It's worth noting, however, that the effect will be relatively short-lived.

Is your pico open or sealed to reduce evaporation? It sounds like it's not getting very good gas exchange.

Thanks for your help. The picos hooked up to a canister which blows ripples across the surface. The surface is only 6" diameter. As far as I know, it is quite common for picos to run very low pH. So far, the corals are very happy.

Randy Holmes-Farley said:
100 mL of saturated limewater added to 10 liters of reef aquarium water will likely instantly boost pH in the whole tank by about 0.5 pH units. It will also boost alk by 1.15 dKH. That's too much at once for either pH or alk, IMO.

Ok thank you Randy. This does give me some wiggle room though since I do not need that much KH boost right now anyway. I will extrapolate from your numbers and figure out a reasonable daily dose of kalk. I'm thinking probably 20 mL would be sufficient which would instantly boost pH by about 0.3 pH units which may be acceptable.

Thinking more, I could quite inconspicuously add a dosing hose and use a doser to split up the kalk. This may be my best option. I was expecting to have to add more kalk than the top up volume. I do have an old analog doser laying around that does 1.6 mL per minute.

Ok problem solved! Thanks everyone!

Randy Holmes-Farley · Mar 20, 2018

Myka said:
The calculator give values for Ca and KH, but it doesn't actually give pH values.Thanks for your help. The picos hooked up to a canister which blows ripples across the surface. The surface is only 6" diameter. As far as I know, it is quite common for picos to run very low pH. So far, the corals are very happy.Ok thank you Randy. This does give me some wiggle room though since I do not need that much KH boost right now anyway. I will extrapolate from your numbers and figure out a reasonable daily dose of kalk. I'm thinking probably 20 mL would be sufficient which would instantly boost pH by about 0.3 pH units which may be acceptable.

Thinking more, I could quite inconspicuously add a dosing hose and use a doser to split up the kalk. This may be my best option. I was expecting to have to add more kalk than the top up volume. I do have an old analog doser laying around that does 1.6 mL per minute.

Ok problem solved! Thanks everyone!