Yesterday’s post regarding the ins and outs of reef aquaria prompted some antagonistic comments regarding my statement that the balling method and automated two part is currently in-trend, making the staple calcium reactor out of trend. Although no justification is needed for such statement, I was under the impression that this early shift was well [...]
Yesterday’s post regarding the ins and outs of reef aquaria prompted some antagonistic comments regarding my statement that the balling method and automated two part is currently in-trend, making the staple calcium reactor out of trend. Although no justification is needed for such statement, I was under the impression that this early shift was well understood by most. It correlates to the availability of trusted dosing pumps and less costly additives (E.g. DIY 2 Part).
This article will not rehash what has been covered many times in books and various publications, rather the intended goal is to highlight the current pros of cons of two part / the balling method and Calcium Reactors for aquarists deciding which method to choose and what equipment is available. Beyond a couple German models, Calcium reactors have not changed much. Accordingly, more of the focus is on two-part and the balling as this seems to be where many aquarists are not familiar.
For some background information on these supplementation methods and the role of calcium and alkalinity, please see the following articles by Randy Holmes Farley—an expert chemist and tremendous asset to the hobby:
- Calcium and Alkalinity
- Selecting a Supplementation Method (Dated regarding products, but a good read)
Like kalkwasser, calcium reactors are a balanced additive solution. Meaning they supplement the aquarium with a 1:1 ratio of calcium and alkalinity (20ppm Ca : 2.8dkh Alk). Calcium reactors rely on the addition of CO2 to create an acidic environment and dissolve calcium carbonate skeletons in the reactor. As such, the low pH effluent can suppress the aquarium’s overall pH. To combat this kalkwasser (Limewater, known as Calcium Hydroxide) reactors are often used to create an extremely stable and time-tested supplement scheme. Saturated kalkwasser is extremely high in PH, but people often forget that kalkwasser actually “captures” CO2 to alleviate the pH suppression initially created by the calcium reactor– shown below we see that the addition of calcium hydroxide (CaOH) uses CO2 and forms calcium and bicarbonate (alkalinity) in red.
Ca++ + 2(OH-) + 2(CO2) <–> Ca++ + 2(HCO3-)
Calcium reactors often scare newer aquarists with their high start up costs and seemingly difficult gadgetry, and it is no secret some calcium reactors can be a major pain to dial in and constantly adjust. However, some well designed reactors (e.g. GEO, MTC Pro Cal) are truly set-and-forget and can be extremely effective by providing a constant supplementation creating parameter stability.
CaRx Media
Nearly all brands have phosphates in the calcium carbonate, adding a minute, but constant source of nutrients to the system. This can be prevented by soaking the media in 0 TDS RO/DI water prior to use or utilizing a small po4 media chamber to absorb any phosphate coming from the effluent. [Certain new reactor models are beginning to implement this.]
CaRx Costs
For reef aquariums with less supplementation needs the costs associated with these reactors can quickly exceed the benefits. The cost of using a calcium reactor is heavily weighted on the initial purchase, with CO2 refills and media replacement costing very little. A good calcium reactor package to get you started will run you nearly $600 to $1,000+ depending on size. For large aquariums the start up cost can be a drop in the proverbial bucket.
Two Part
The two part method of supplementation has been widely used for many years, but with the 2004 and 2006 DIY articles outlined by Randy Holmes Farley this method has flourished due to its low cost. Unlike, kalkwasser and calcium reactors, two part is not a balanced additive out of the bottle, rather the calcium and alkalinity solutions are added independently and aquarists can make it balanced. Two part is often coupled with a solution of magnesium chloride and magnesium sulfate to supplement magnesium levels making the method three parts.
To add further complication we also have the Balling Method. The Balling Method is a spin off of two part and can be easily confused with the various names, e.g. Balling Light and Balling Full. To learn how the Balling Method differs from two part please see here: The Balling Method, How it Differs from Two Part.
Precision and Control
The greatest benefit of two part is control, but it can also be its greatest con. It is up to the aquarists to measure calcium and alkalinity levels and dose accordingly. Thankfully we have Jose Dieck’s reef chemistry calculator that addresses nearly all popular supplements making this much easier. Once the amount of calcium and alkalinity solutions required is calculated, the dosing can become quite simple via hand dosing… or better yet automated with dosing pumps. Dosing pumps bring the stability and hands-off-benefit of calcium reactors to the two part or balling method. Dosing pumps can be fairly expensive at roughly $70-$200 per pump head depending on the brand and model. [We are currently reviewing a new unit that utilizes 4 pumps for near complete dosing control.] Look for dosing pumps with a minimum of 1 ml per minute. Certain brands are notoriously inaccurate and by design can create siphons. Always calibrate each pump and if your set up can allow siphons check valves are a worthwhile addition.
The precision that two part offers can be a large benefit for those wishing to keep strict parameters. While balanced additives like calcium reactors, make “dosing easy” they supply a fixed ratio of calcium and alkalinity, if that ratio is skewed the calcium reactor will only maintain that ratio. Additional supplements like two part will be needed to adjust to desired levels. This may not seem like much of a concern for most, but can be an issue for those seeking ”natural saltwater” (NSW) parameters. Millero’s Chemical Oceanography is often cited for it’s measured ocean surface water parameters:
- 420ppm Calcium
- 2.5 meq/L or 7dkh Alkalinity
- 1280ppm Magnesium
- 34-36ppt Salinity
- 8.1-8.3 pH
These are also considered ideal parameters by many SPS keepers, but unfortunately very few synthetic salt mixes hit these levels at 35ppt. For example Reef Crystals at 35ppt is known to match NSW with a Calcium level of 420ppm, but hits 12dkh for Alkalinity! Hobbyists employing frequent water changes should not fret over such a change (5dkh). However, larger waterchanges could create problems in delicate SPS reefs and create more work when adjusting parameters.
Assuming those tested levels are accurate, calcium would need to be raised ~35ppm to match NSW ratio and aquarium levels would be slightly elevated. Aquarists must be mindful that water changes are often a source of calcium and alkalinity supplementation from their increased levels.
Additionally, with two part or the balling method we can quantifiably adjust calcium and alkalinity levels to a desired level. For example, when removing a large Acropora or Tridacna, the reduced demand can be estimated and the solution amount can be reduced. This can be done with Calcium Reactors, but generally with less precision.
(We often forget that there is much more calcium than alkalinity in our seawater, and sometimes a low alkalinity level is not attributable to an imbalance, but is a sign that more calcium and alkalinity is needed. A drop of 1.4dkh in alkalinity corresponds to only a 10ppm drop in calcium!)
Salinity Increase from Na & Cl
As stated earlier the major issues with calcium reactors surround initial cost and pH suppression, while two-part passes these areas with good marks it is not perfect. When large amounts of Calcium Solution (CaCl) and Alkalinity solution (NaHCO3) are added the residual ions (sodium and chloride) can build up to increase salinity. This can be countered easily with frequent water changes, but it is something to be aware of. Other potential issues include purity. The low cost of two part generally means making your own solutions, that are generally not intended for aquarium use.
Which is better?
Two part and Calcium Reactors are both proven to work well for aquarists, so which is better? Both get the job done making this question highly subjective and unique to the individual. The largest concerns are comfort with the equipment, cost, and supplementation demand.
With the economic state we are in, cost is likely a heavily weighted factor. A 200+ gallon high calcium and carbonate demand system will be well suited for calcium reactor use, where a 30g heavy-demand system is likely a better candidate for two part / balling either manual or automatic. Calcium reactors become a better economic choice on larger systems because the long term supplementation costs (Co2 and Ca Media) are inexpensive. (The same can be true for those buying Two Part chemicals in bulk.) See Jose Dieck’s charts below that compare costs of different size systems and their alkalinity supplementation requirements. (Initial purchase price is depreciated straight-line over 5 years with no salvage, e.g. $750 reactor / 5 years = $150 cost per year. This is roughly the start price used for Calcium Reactors when dkh=0).
Trends
Now that quality dosing pumps are becoming more available and the price of the two part solutions have come down, we are seeing a shift by many experienced aquarists away from calcium reactors and towards balling and automated two part. This can be economically justified depending on the system, but without a doubt dosing pumps and the balling method are a trend of the moment and rightfully so as it is being acknowledged as something “new”. Trends do not mean one item is better than an other, they don’t make anything obsolete. Both Calcium Reactors and Two Part are here to stay and if done properly either one can be a great choice.
For additional reading and resources on the topic:
