Halting Kalkwasser for Tank Upgrade

Jizu Puentes · Jan 27, 2016

I am on the last leg of upgrading my system and getting everything ready for the "moving day" Ive got all my plumbing, powerheads, lights etc ready to go. While drilling holes at work and think of my reef (as always) I started to think about my kalkwasser usage. My current system is a 110 display and a 55 sump. Currently the system replaces about a gallon of evaporated water with kalkwasser at 1tsp/gal a day. With the current uptake of kalkwasser my Ca measures 430 and my Alk 10. The new tank will be a 135 and the 110 will be plumbed to it as a macroalgae grow out. Also there will be a 60 gallon frag tank in the same system. The question that formed in my head was that if I am adding all of this water volume then will the available Ca be high enough to stop kalk use for now? Wouldnt the use of kalk when it isnt needed cause my ca and Alk levels to rise?

Randy Holmes-Farley · Jan 27, 2016

Jizu Puentes said:
Wouldnt the use of kalk when it isnt needed cause my ca and Alk levels to rise?

Yes to that.

No to the idea that larger water volume will somehow mean you need less limewater. If all that happened is the water volume went up ten fold but the creatures remained the same and grew the same, you'd need exactly the same amount of limewater to meet the demand and keep calcium and alkalinity unchanged.

What happens is that without dosing the values (like dKH) drop more slowly, but they also rise more slowly when dosing. These exactly offset.

Jizu Puentes · Jan 27, 2016

Ok I was thinking that when the corals uptake exceeded the amount in the volume of water then you'd need dosing. For example is you put a small sps in say a 30 gallon tank you wont need to dose but if you put a large colony in you would. I thought that having such a large volume of unused saltwater would mean that it would take longer for my current corals to exhaust the nutrients available.

Randy Holmes-Farley · Jan 28, 2016

Jizu Puentes said:
Ok I was thinking that when the corals uptake exceeded the amount in the volume of water then you'd need dosing. For example is you put a small sps in say a 30 gallon tank you wont need to dose but if you put a large colony in you would. I thought that having such a large volume of unused saltwater would mean that it would take longer for my current corals to exhaust the nutrients available.

Yes, longer to exhaust them, but it will then take more supplement to bring it back to the same starting value in the larger volume, even if the measured drop was smaller. So in terms of dosing there is no change in the required amounts.

That said, if you are doing water changes with a mix that is above your normal tank parameters, and continue to do the same PERCENTAGE volume water changes, then each change will bring in more than before since it is larger, so water changes alone might be able to handle more corals than with smaller water changes. But this effect is usually minimal for an SPS tank unless the salt mix parameters are far above the tank parameters and then usually only for magnesium where the demand is so low. Rarely would it be enough for alkalinity in an SPS tank, unless the changes are on the order of 30-50% daily.

Jizu Puentes · Jan 28, 2016

Randy Holmes-Farley said:
Yes, longer to exhaust them, but it will then take more supplement to bring it back to the same starting value in the larger volume, even if the measured drop was smaller. So in terms of dosing there is no change in the required amounts.

That said, if you are doing water changes with a mix that is above your normal tank parameters, and continue to do the same PERCENTAGE volume water changes, then each change will bring in more than before since it is larger, so water changes alone might be able to handle more corals than with smaller water changes. But this effect is usually minimal for an SPS tank unless the salt mix parameters are far above the tank parameters and then usually only for magnesium where the demand is so low. Rarely would it be enough for alkalinity in an SPS tank, unless the changes are on the order of 30-50% daily.

Thanks that was the perfect way to explain it.