comparing chemistry re kalkreactor v. calcium reactor...

[Sk8r]

...re safety, reliability, potential for disasters, and how the chemistry actually works, pro or con. I was rather torn about posting this query here or in Equipment, but I think the question is more...how far can I trust such systems to keep the tank better than I can by hand-adding? Naturally dkh alk and calcium are going to have peaks and valleys with hand-adding...but how much trouble can you get into with the automation? And is one better than the other for stability?

System: 54g tank, 30g sump, high flow, high evaporation, corals and fish with aragonite sand, live rock.

[jdieck]

If the systems are properly designed you shall have no trouble with neither.
A Calcium reactor system usually require the reactor, a PH monitor or controller, a CO2 cylinder, a CO2 regulator with solenoid and a water feed powerhead
A Kalk reactor system usually require an adjustable flo dosing pump, an RO/DI water reservoir, the reactor and a float switch system to turn on or off the doser as required by the evaporation.
Chemistry wise In a Calcium Carbonate reactor, the low PH 6.4 to 6.8 created by the addition of CO2 will dissolve the Calcium Carbonate media forming a combination of Carbonic Acid and Bicarbonate as well as Calcium ions in a balanced ratio of 20 ppm Ca per 1 meq/lt of alkalinity. The amount of Alkalinity addition (and thus the Calcium) is adjusted by adjusting the amount of effluent flow as well as the amount of CO2 added.
The Carbonic Acid and some unreacted dissolved CO2 carried over in the effluent will tend to lower the tank PH. Tanks running properly sized Calcium reactor usually run between 8.0 and 8.1 PH
A calcium reactor capacity is only limited by the size of the reactor.
In a Kalk reactor the Calcium Hydroxide (Lime) will react with CO2 dissolved in the water to form Calcium and Carbonate ions which will supplement the Calcium and alkalinity in a balanced ratio of 20 ppm calcium per 1 meq/lt of alkalinity. Tanks supplied with Kalk reactors usually run a PH between 8.2 and 8.5
Note that the consumption of CO2 is what increases the tank PH.
The maximum amount of Alkalinity (and thus Calcium) you can add with a Kalk reactor is limited by the amount of evaporation in the system. With a Kalk reactor you can not adjust the strenght (concentration) of the lime water so if less alkalinity is required than would be added by the evaporation, limiting the dosing via flow adjustment will be required while a pure water top off could handle the additional top off required
In large systems with a lot of consumption is sometimes advisable to run both a calcium reactor and a Kalk reactor to maintain a more stable PH.
The folllowing chart can give you an idea of how much alkalinity you can add depending on the % of evaporation.
http://reef.diesyst.com/Evaporation.gif

[Sk8r]

THank you, JDieck---very helpful! I'm sort of leaning to a kalk reactor, since it requires less equipment that I *don't* have, seems to have some fewer pieces...and once I establish what the evaporation rate is on this new setup, that will help me make up my mind.

[jdieck]

Most fully stocked SPS and clamp tanks consume between 2 and 3.5 dKh per day, that calls for an evaporation of 1.75 to 3% of the system volume. Normal tank evaporation range from 1.5 to 2% If chilled evaporation rarely reaches 1%