Dosing options for a reef

[Jarred1]

I am currently setting up an Sps reef and I have been doing a lot of reading about dosing options and I have come down to two possibilities.

My first option is dosing two part, I read Randy Holmes Farly's essay on dosing two part and noticed that he said when dosing with balanced two part solutions you should dose both parts in equal amounts. When I test my tank though I find that
mug tank uses more Alk than cal. I also remember reading why it happens and it still doesn't make sense to me. I also read that you should dose part A and part B a few hours after you dose one of the parts because when dosing them together they will bind with each other making both parts useless. Is that true?

The second thing I could do is top the tank of with kalkwasser. The problem I see with that is how much kalk do I need to the top off water? I don't have a sump so I will have it topped off into a high flow area, what kind of pump could I use? I used to have a air pressure system for one of my told tanks and snails used to get on to the float switch and get it stuck on causing an over dose ( thankfully nothing bad ever happened from it). If the tank isn't using the same amount of Alk and cal the perimeters will become unproportional, right?

Any help would be greatly appreciated!
Jarred


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[APBonds]

When you are dosing cal it drops alk of your tank, so it is said when you dose equal parts to off set the drop. But I have found I need to add a few ml more of alk to keep up with what the corals are using. The extra amount of alk that I dose is very little, my cal pump runs 40 sec may alk pump runs 43 sec. Start out with equal amounts test your water and adjust your alk dose to keep up with the demand of your tank.

 

[Jarred1]

Right now my Alk is at 8 dkh and my cal is at 450, I don't want to raise the cal right now because I think it is already to high.


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[Randy Holmes-Farley]

My first option is dosing two part, I read Randy Holmes Farly's essay on dosing two part and noticed that he said when dosing with balanced two part solutions you should dose both parts in equal amounts. When I test my tank though I find that
mug tank uses more Alk than cal. I also remember reading why it happens and it still doesn't make sense to me. I also read that you should dose part A and part B a few hours after you dose one of the parts because when dosing them together they will bind with each other making both parts useless. Is that true?

T

It is OK to dose unequally, but often it is not optimal to do so because you really need both parts equally even if you do not see it initially.

That is generally for one of two reasons. One is many salt mixes start with excessive calcium, so you do not really notice calcim dropping because it is so high and water changes keep pushing it up.

The second is a trick of the math involved. Here's a cut and paste from one of my article on this topic:

When Do Calcium and Alkalinity Demand Not Exactly Balance?
http://reefkeeping.com/issues/2004-12/rhf/index.htm

Calcium and Alkalinity Demand: Calcium Carbonate Mathematics

Calcium carbonate formation consumes its two components in an exact 1:1 ratio. In the units used by aquarists, this ratio corresponds to one meq/L (2.8 dKH; 50 ppm CaCO3 equivalents) for every 20 ppm of calcium. Not surprisingly, this is also the ratio of alkalinity to calcium that is supplied when calcium carbonate is dissolved, as in a CaCO3/CO2 reactor. Fortuitously for the aquarist, this is also the ratio supplied when calcium hydroxide is dissolved, as with the use of limewater (kalkwasser).

Apparent Excess Demand for Alkalinity

One of the most common complaints of new aquarists is that their aquaria seem to need more alkalinity than their balanced additive system, such as limewater, is supplying. While there are reasons this may actually be the case over the long term (these will be detailed later in this article), frequently these aquarists are seeing a "chemical mirage" rather than a real excess demand for alkalinity.

One of the interesting features of seawater is that it contains a lot more calcium than alkalinity. By this I mean that if all of the calcium in seawater (420 ppm; 10.5 meq/L) were to be precipitated as calcium carbonate, it would consume 21 meq/L of alkalinity (nearly 10 times as much as is present in natural seawater). In a less drastic scenario, let's say that calcium carbonate is formed from aquarium water starting with an alkalinity of 3 meq/L that it is allowed to drop to 2 meq/L (a 33% drop). How much has the calcium declined? It is a surprise to many people to learn that the calcium would drop by only 20 ppm (5%). Consequently, many aquarists observe that their calcium levels are relatively stable (within their ability to reproducibly test it), but alkalinity can vary up and down substantially. This is exactly what would be expected, given that the aquarium already has such a large reservoir of calcium.


So the first "deviation" from the rule of calcium and alkalinity balance really isn't a deviation at all. If an aquarist is supplying a balanced additive to his aquarium, and calcium seems stable but alkalinity is declining, it may very well be that what is needed is more of the balanced additive, not just alkalinity. This scenario should be assumed as the most likely explanation for most aquarists who should look for more esoteric explanations for alkalinity decline only if calcium RISES substantially while alkalinity falls. Likewise, if alkalinity is rising and calcium seems stable when using a balanced calcium and alkalinity additive system, the most likely explanation is that too much of the additive system is being used.

The real imbalance effects described later in this article take effect slowly, and are manifested over weeks, months and years. This short term "chemical mirage" caused simply by the mathematics of calcium and alkalinity additions can be seen in a single addition. Any effect that develops rapidly over the course of a few days is almost certainly not a true imbalance.

The following scenarios show what can happen to a reef aquarium whose dosage with a balanced additive system does not match its demand. Table 1 shows what can happen when the dosing is inadequate. Alkalinity drops fairly rapidly. After two days, many aquarists might conclude that they need additional alkalinity, when in reality, they need more of both calcium and alkalinity to stabilize the system.

Table 2 shows what happens when too much of a balanced additive is added. After a few days, many aquarists would conclude that alkalinity is rising too much, but that calcium is fairly stable. Again, what is needed is less of the balanced additive, not just less alkalinity.