Zoas losing color...

J Fox · Mar 29, 2016

I have a small colony of Vulcan Blood Zoas that were doing so well, went from 8 to 11 polyps so fast after putting them in our tank. Lately though they are not as bright as they were it seems.
After reading here I am wondering is my water too clean ? I do have algae growing - and put one drop of Coral Vitalizer in every other day.
Phosphates are 0
Nitrates are 0.75
PH 8.2
80 degrees
Also Shazam Paly has added 5 polyps since going in a month ago. So things are growing..
And advice would be great - thank you.

TheEngineer · Mar 29, 2016

What's your alk and calcium?

J Fox · Mar 29, 2016

Guess I need more test kits - I don't know. As a newbie to this hobby, thought that only pertained to hard or Stoney corals. I can get kits and test those.

TheEngineer · Mar 29, 2016

They are important for soft corals too.

TheEngineer · Mar 29, 2016

From @Randy Holmes-Farley 's article: http://reefkeeping.com/issues/2004-05/rhf/

Calcium

Many corals use calcium to form their skeletons, which are composed primarily of calcium carbonate. The corals get most of the calcium for this process from the water surrounding them. Consequently, calcium often becomes depleted in aquaria housing rapidly growing corals, calcareous red algae, Tridacnids and Halimeda. As the calcium level drops below 360 ppm, it becomes progressively more difficult for the corals to collect enough calcium, thus stunting their growth.

Maintaining the calcium level is one of the most important aspects of coral reef aquarium husbandry. Most reef aquarists try to maintain approximately natural levels of calcium in their aquaria (~420 ppm). It does not appear that boosting the calcium concentration above natural levels enhances calcification (i.e., skeletal growth) in most corals. Experiments on Stylophora pistillata, for example, show that low calcium levels limit calcification, but that levels above about 360 ppm do not increase calcification.3 Exactly why this happens was detailed in a previous article on the molecular mechanisms of calcification in corals.

For these reasons, I suggest that aquarists maintain a calcium level between about 380 and 450 ppm. I also suggest using a balanced calcium and alkalinity additive system for routine maintenance. The most popular of these balanced methods include limewater (kalkwasser), calcium carbonate/carbon dioxide reactors, and the two-part additive systems.

If calcium is depleted and needs to be raised significantly, however, such a balanced additive is not a good choice since it will raise alkalinity too much. In that case, adding calcium chloride is a good method for raising calcium.

Alkalinity

Like calcium, many corals also use "alkalinity" to form their skeletons, which are composed primarily of calcium carbonate. It is generally believed that corals take up bicarbonate, convert it into carbonate, and then use that carbonate to form calcium carbonate skeletons. That conversion process is shown as:

HCO3- à CO3-- + H+

Bicarbonate à Carbonate + acid

To ensure that corals have an adequate supply of bicarbonate for calcification, aquarists could very well just measure bicarbonate directly. Designing a test kit for bicarbonate, however, is somewhat more complicated than for alkalinity. Consequently, the use of alkalinity as a surrogate measure for bicarbonate is deeply entrenched in the reef aquarium hobby.

So, what is alkalinity? Alkalinity in a marine aquarium is simply a measure of the amount of acid (H+) required to reduce the pH to about 4.5, where all bicarbonate is converted into carbonic acid as follows:

HCO3- + H+ à H2CO3

In normal seawater or marine aquarium water, the bicarbonate greatly dominates all other ions that contribute to alkalinity, so knowing the amount of H+ needed to reduce the pH to 4.5 is akin to knowing how much bicarbonate is present. Aquarists have therefore found it convenient to use alkalinity as a surrogate measure for bicarbonate.

One important caveat to this surrogate measure is that some artificial seawater mixes, such as Seachem salt, contain elevated concentrations of borate. While borate is natural at low levels, and does contribute to pH stability, too much interferes with the normal relationship between bicarbonate and alkalinity, and aquaria using those mixes must take this difference into account whendetermining the appropriate alkalinity level.

Unlike the calcium concentration, it is widely believed that certain organisms calcify more quickly at alkalinity levels higher than those in normal seawater. This result has also been demonstrated in the scientific literature, which has shown that adding bicarbonate to seawater increases the rate of calcification in Porites porites.4 In this case, doubling the bicarbonate concentration resulted in a doubling of the calcification rate. Uptake of bicarbonate can apparently become rate limiting in many corals.5 This may be partly due to the fact that both photosynthesis and calcification are competing for bicarbonate, and that the external bicarbonate concentration is not large to begin with (relative to, for example, the calcium concentration).

For these reasons, alkalinity maintenance is a critical aspect of coral reef aquarium husbandry. In the absence of supplementation, alkalinity will rapidly drop as corals use up much of what is present in seawater. Most reef aquarists try to maintain alkalinity at levels at or slightly above those of normal seawater, although exactly what levels different aquarists target depend a bit on the goals of their aquaria. Those wanting the most rapid skeletal growth, for example, often push alkalinity to higher levels. I suggest that aquarists maintain alkalinity between about 2.5 and 4 meq/L (7-11 dKH, 125-200 ppm CaCO3 equivalents), although higher levels are acceptable as long as they do not depress the calcium level.

Alkalinity levels above those in natural seawater increase the abiotic (nonbiological) precipitation of calcium carbonate on objects such as heaters and pump impellers. This precipitation not only wastes calcium and alkalinity that aquarists are carefully adding, but it also increases equipment maintenance requirements. When elevated alkalinity is driving this precipitation, it can also depress the calcium level. A raised alkalinity level can therefore create undesirable consequences.

I suggest that aquarists use a balanced calcium and alkalinity additive system of some sort for routine maintenance. The most popular of these balanced methods include limewater (kalkwasser), calcium carbonate/carbon dioxide reactors, and the two-part additive systems.

For rapid alkalinity corrections, aquarists can simply use baking soda or washing soda to good effect.