An article on alkalinity is featured, a re-write on an earlier article by DBW, and all the OZ REEF Park news is reported.

Editorial

Welcome once again to OZ REEF Press. I tell you what, these reef aquariums certainly help you to use up all that spare time that you may have. And ever bit of it will be used up for me over the next couple of months as I have several projects that have to be done and finished before it starts to get too hot. This includes finishing the calcium reactor (more on that later), build two thermostats for the ventilation fans and chiller, complete the chiller, and design and construct a combined surge device and external refugium. And as soon as I get these things built and some plans done you can be sure to see them here online :-). On a sad note, his month has not been the best one on the resident side of things. Have lost a few of the residents to various occurances, which is just a bit depressing. See the Bereavement Notices below for more information.

But there is some good, well actually great news :-) The cleaner shrimp eggs have hatched!!!! Wahoo, I'm a grandfather ;-), well was for a short time anyway. Anway, about 1 hour after the lights turned off I grabbed the torch for my nightly look around the reef to check things out. I do this just to have a look around and see some organisms that you just don't see during the day. While looking around and along the bottom of the tank a very strange and small object floated through the torch beam. It was club shaped and was gyrating through the water. Apon closer inspection I realised it was a baby shrimp about 2mm long, and how cute he was ;-). You could actually see the legs, tail and a main set of claws. It was all there just like "Muma and Popa" ;-). The majority of the body was transparent, with a white patch in the abdominal region. There was quite a few floating around in the water, I cannot really hazard at a guess to how many as I really have no idea. Within about an hour of spotting them though, almost all of them were gone. I suspect that most of them would have either caught by some of the night feeding corals, minced up by the circulation pumps or eaten by some other organisms in the Park. In the morning I noticed that the eggs on one of the cleaner shrimp had gone green, which appears to indicate that they are close to maturity. The second shrimp I was unable to get a close look at as was hiding towards the back of the reef structure. And this is due to the fact that it had just molted after releasing the larvae. So it now appears that I have a regular supply of planktonic larvae for the night feeding corals to feast on. Of course I will keep you all posted on what is happening.

It has just become apparent that after the bi-weekly water change that micro algae growth, particularly that which coats the glass as this is easy to see, accelerates. During the 1^st week after the water change the glass has to be cleaned 2-3 times to maintain good viewing clarity of the Park. Then in the 2^nd week only 2 are required. I also missed one weeks change, therefore it was with out the water change for 3 weeks. During this 3rd week the glass only had to be cleaned once. Will have to monitor the Park's behavior more closely with respect to this to see if it may benefit from longer periods between the water changes.

After the addition of the live sand last month, the copepod population has soared. Unsure whether this is actually a direct consequence of adding the live sand or the population reached a critical point and increased to a visible/noticable level. But considering the fact that the live sand was added, then about a week later copepods started appearing everywhere seems to be a bit more than a coincidence. Until this time I had only spotted isopods and some worms. Now copepods can be seen within the tank at night, and in the sump at all times. I have placed a thin layer of sand in the sump to act as a sort of refugium. Additionally this is acting as a place to hold aggressive critters that I have caught in the main display tank.

Talking about aggressive critters, and what a paragraph connection that is ;-), an unauthorised black true crab was apprehended during the last month. Earlier this month I spotted a rather large black claw being waved at one of the fire shrimp while feeding the reef. In order to catch this guy the four shrimp had to be removed to breeding traps hanging on the side of the tank. This is so that the shrimp would not end up being caught in the trap set for the crab. The trap consisted of just a 600ml plastic soft drink bottle with the top cut off and string attached to the sides to make it easy to pull out of the tank. Bait of shrimp and scallops were placed in the bottom of the bottle, and it was leaned against a rock near where the crab was spotted. It took several nights, but finally one morning there was a black crab sitting in the bottom of the trap trying desperately to climb out of the bottle. A picture should be online shortly, along with a heap of other new pictures as well. He has now taken up residence in the sump along with all the copepods, where he can do no harm.

Some of the corals are still growing well, including the Acropora sp. fragments (but there has be some slowing in the growth rate here, and am yet to determine the reason why) and two colonies of Blastomuss wellsi. Both of the Blastomuss wellsi colonies have started to bud, with each only having 5 polyps when they moved into the Park. Now small daughter polyps are appearing around the base of each of the original polyps. At a guess it appears like there would be around 4-8 new polyps around the base of each of the parents. The mushroom anemones appear to be going well as well, with several of them fragmenting into two anemones. One of the species of mushrooms has a very unusual method of reproduction, with the large polyp moving position on the rock and then leaving behind a small bit of flesh that then develops into a new anemome. The zoanthids, all three different species, are now growing very well. Almost every rock in the reef structure has zoanthids on them, and in the case of quite a few of them the upper surface is 100% covered.

This last month has been the first time that I have heard a clicking noise coming from within OZ REEF. Awhile ago I did see a mantis shrimp running around the tank and sticking its head out of the odd hole in the rock. The clicking noise can indicate a pistol or mantis shrimp within the tank. They both make a similar noise but the method of generating this noise is different. The pistol shrimp makes it by opening and closing one of its claws, the larger one, and it typically occurs in pairs, opening and closing of the claw. They use this techinque to stun their prey by the resulting shockwave. Mantis shrimp on the other hand make the noise by physically hitting the rock with their "mantis" like claws. This is the mechanism they use to stun their prey before consuming them. So far I have only heard single, or double clicks, so there may also be a pistol shrimp in the tank. But I do know that there is a mantis shrimp in there, how I am going to get him out is bit of a problem too :-(.

And finally I have just finished the calcium reactor, and should have it connected and operating shortly. Very, very simple to make this one too. I am currently testing out the unit on town water to see if the yeast CO₂ generating technique will sufficent to supply a consistant enough amount of gas. I suspect that it may, but it could be a bit fiddly. I aim to give it a good try, but if I fail I have a supply of bottled CO at not a bad price lined up. Details will be in the DIY Plans section shortly, with there already being a parts listing there now.

Well, that is it for this month once again. If anyone has anything that they think needs to have an article written on that is not explained clearly anywhere else on the net then let me know. I am always on the look out for subjects that have not been treated very well yet. Oh yeah, if you happen to have a DIY project that you have completed yourself and are looking for somewhere to put them online then just give me a yell and I will see what I can do for you :-) Catch ya,
DBW.

Welcome OZ REEF's New Residents

• 9 x ????, Hermit Crabs. These are the white/grey ones that I already have introduced into the Park. All of them are under 10mm across in total, excluding the shell. Very niced sized hermits.
• 7 x ????, Snails. Unsure on the type here, but already had one and he was doing a good job so got some more. So far the majority of them have stayed on the front glass and kept it very clean.
• 1 x Acropora sp., Staghorn Coral. A very different looking species as the skeleton is fairly smooth except where the polyps are located which raises up slightly. Is dominantly brown but has a very nice bright green tinge that can be seen quite easily.
• 1 x Acropora sp., Staghorn Coral. Pink or skin pink coloured flesh with a light green tinge. Fragmented this one into three colonies, and they are spread across the length of the Park.
• 1 x ????, Zoanthid Colony. Another different type of zoanthid that I saw in the corner of a store tank and got thrown in for free :-).
• 1 x Tridacna maxima, Maxima Clam. Very nice one, with some green around the edge of the mantle. But this one appears in the Bereavement Notices too :-(.

Resident of the Month

Dear Marther ReefKeeper

Dear Marther,

I have noticed on the odd occasion some of my fellow Cnidarian residents have been expelling a long, brown, stringy mucus. It usually appears during the middle of the day, and it is typically only restricted to one or two residents at a time. And each one has settled in and has been living in the Park for atleast 2 months, and there has been no fluctuation in the environmental parameters, such as light and temperature. What is happeing here, and should I be concerned about my own health if it is contageous?

From,
Concerned Neighbour

Dear Concerned Neighbour,

You have no need to concerned. This is indicated by the fact that it has occured after your fellow resident has been well settled in and there has been no environment fluctuations. These effects I have discussed before, and can cause the expelling of the zooxanthellae. What is happening in this case is the expulsion of the zooxanthellae, but this time for a different reason, or wastes. With the zooxanthellae, they are being expelled as the population has grown too large for the polyp. The the numbers have to be cut down to avoid poisoning due to excess waste and nutrients as produced by the zooxanthellae. Additionally because a coral polyp has only one opening, then both food and wastes must by exchanged through the one hole. After a polyp has finished its meal then the left overs will be ejected through the mouth. But if this expulsion keeps on going, then there may be another cause.

From,
Marther ReefKeeper

Tom's Bit

by Thomas S. Heo

Sorry, but Tom is very busy with his new job. He is off being a big advertising/web designer ;-). He assures me that he is intending to keep writing articles for here, so we will have to wait until he has some spare time.

Special Feature

Alkalinity

by

What is alkalinity?

Alkalinity is a measure of the pH buffering capacity of a solution, usually applied to seawater by marine aquarists. In this case is not used in the typical chemistry context, in which it is used to indicate that the solution has a pH above 7.0, i.e. it is basic or alkaline. Alkalinity indicates the concentration of the following list of anions:

• carbonate, CO₃^2-
• hydrogen bicarbonate, HCO₃^-
• borate, BO₃^3-
• sulphate, SO₄^2-
• hydroxide, OH^-

The value given as the alkalinity of the water is determined by the amount of free acid, or hydrogen ions (H⁺), required to neutralise all of the above anions. The common units used to measure alkalinity are meq/l (milli-equivalent per litre) and dKH (degree of carbonate hardness).

Why is alkalinity important?

Alkalinity is what provides the correct and stable pH for a reef aquarium if it is maintained at sufficient levels. A correct and "stable", i.e. without wide fluctuations, pH is important for the health of a reef aquarium's inhabitants. Many authors state that alkalinity is important as it is a measure of the ability to resist a drop in pH. This is true, but it is really only half of the story. It is also a measure of the ability to resist an increase in the pH. The "buffering" of the water works in both directions, increasing and decreasing pH. Some components of the alkalinity buffer system are also utilised by organisms, such as hard corals, and so have to be present in sufficient amounts for good health and growth of the organism. Additionally, the higher the alkalinity, the greater the ability of the water to absorb the addition of an acid or a base with only small change in the actual pH, more on this later. Alkalinity levels of 3.0 to 6.0 meq/ml are recommended to keep a stable pH in a reef aquarium, with the range of 2.5 to 3.5 meq/ml being a typical level for natural seawater.

How does a buffer work?

A buffer is a series of chemical species in solution that resists a change in pH when either a base, e.g. hydroxide ions (OH^-), or an acid, e.g. hydrogen ion (H⁺), are added to a solution. It keeps the pH almost constant by acting as a reservoir for H⁺, donating them to the solution when the H⁺ concentration falls and taking them from the solution when the concentration rises. The buffering system involves a base and an acid in relatively high concentrations, and in equilibrium with each other. The base acts as a H⁺ absorber and the acid as a H⁺ donator. When this equilibrium is upset by the addition of H⁺ or OH^- (the addition of hydroxide in effect removes H⁺) to the water, then the acid and base alter their concentrations until equilibrium is again achieved. When this equilibrium is attained the pH is very close to the original pH when compared to the value that would have been attained without the buffer system present.

The carbonate buffer system

It is possible to buffer a solution at any pH by the choice of an appropriate acid/base pair. For seawater and human blood the important buffering system involves carbonic acid (H₂CO₃), hydrogen bicarbonate (HCO₃^-), carbonate (CO₃^2-) and of course hydrogen (H⁺). The chemical reactions involved are as follows:

(Note: carbonic acid, H₂CO₃, cannot be differentiated from dissolved carbon dioxide, CO_2(aqueous), in solution therefore reaction (1) and (2) are normally combined and the two are considered one and the same and can be interchanged).

The first two reactions, (1) and (2), are much slower than the last two, (3) and (4). The more important reaction for the buffering system is (3). In this particular reaction H₂CO₃, carbonic acid, is acting as the acid and HCO₃^-, hydrogen bicarbonate, as the base. If H⁺ is added to the system the HCO₃^- acts as a base and removes the excess hydrogen ions from solution by forming H₂CO₃. Visa versa will occur if H⁺ is removed from solution, with the H₂CO₃ dissociating and releasing more H⁺ into the solution. The pH is thus stabilised by the equilibrium between the acid and base, adding or removing H⁺ as required. Reaction (4) also performs a similar function, with HCO₃^- being the acid and carbonate, CO₃^2-, the base and reacting similarly as (3) to the addition and removal of H⁺. From this it can be seem that the entire equilibrium system can get very complex, with the formation of one species effecting the equilibrium position of reactions and therefore the concentration of the other species involved. It must also be noted that these are not the only reactions and species involved in the complex buffering of seawater. It also includes borate (BO₃^3-), sulphate (SO₄^2-), and hydroxide (OH^-) and the associated acid/base pair reactions. But in comparison to the carbonate buffering system these perform a minor role and so can typically be ignored.

The relative concentrations of the three main components of the carbonate buffering system (CO₂, HCO₃^-, and CO₃^2-) vary with both pH and temperature. Figure 1 shows the relationship of the relative concentrations with pH, at 25^oC, 1 atm and 35ppt salinity. Over the pH range of 7.0 to 9.0 the relative concentration of CO₃^2- increases with increasing pH, while dissolved CO² decreases, and HCO₃^- passes through a maximum at around pH 7.5. Under the conditions typical of natural seawater, pH 8.3, then the major species present is HCO₃^-, composing 80%, and the remainder CO₃^2-, 20%. Dissolved CO₂ is only present in a very small relative amount. Figure 2 shows the relationship with temperature, at pH 8.3, 1 atm and 35ppt salinity. This shows that as the temperature increases then the relative concentration of HCO₃^- decreases and CO₃^2- increases, with only a minor effect on the dissolved CO₂.

What determines the pH?

The pH of a buffered solution is determined by the ratio of the concentrations of the base and the acid species i.e. [Base]/[Acid]. Therefore as the concentration of the acid increases over that of the base, then the pH will fall and visa versa. This effect can be use to alter the pH of a solution to whatever value is required, within a certain range depending on the acid/base pair. Although it is not quite this simple within the complex system of a reef aquarium. Luckily it is not usually required to worry about this is the correct techniques are used to replenish the alkalinity, as if the alkalinity is maintained at sufficient levels then the pH tends to the natural value of 8.0-8.4.

Figure 1 shows the relative concentration of each of the species with pH, and it can be seen from this what the correct ratio of HCO₃^- and CO₃^2- should be, around 4:1 for pH 8.3. If this ratio is different, then the system will tend to a different pH, such as 2.3:1 the pH will be around 8.5. This information can be used to help return a reef aquarium to its correct pH if it has a tendency to stay at a higher or lower than ideal pH. If the pH is too high, then the ratio of HCO₃^- to CO₃^2- is too low and some more hydrogen carbonate is required. The visa versa is also true, with a low pH indicating a ratio that is too high, so some carbonate is required. These additions can be made or water changes made with water with the correct ratio to return the ratio to the correct value for the required pH.

As the ratio [Base]/[Acid] determines the pH then it follows that it is desired to minimise the change of this ratio upon the addition/removal of H⁺. The buffering capacity, i.e. the ability to absorb the addition/removal of H⁺ with only a small pH change, is determined by the magnitude of the acid and base concentrations. This is easily seen when considering the ratio [Base]/[Acid]; the larger the acid/base concentrations, the smaller the percentage change in these concentrations after the addition/loss of H⁺, resulting in a smaller change in the ratio. Therefore to get the best buffering capacity and maintain a stable pH then this ratio has to remain almost constant. This will occur when the amount of H⁺ that is added/removed is small compared to the concentration of the buffer species. As a result, the higher the concentration of the acid/base buffering species the greater the buffering capacity of the solution. This is why if a high alkalinity level is used, then the aquarium has a more stable pH. It should also be noted that a solution is better able to resist pH changes in any direction if the ratio [Base]/[Acid] is one.

Why does alkalinity decrease?

Alkalinity has a natural tendency to decrease over time in an enclosed system. This is due mainly to two factors: the production of acids as by-products of biological processes, and the utilisation of some of the buffering species by organisms. As biological processes within the organisms held in the reef aquarium proceed, various acid species are generated. With each addition of acid reaction (3) and (4) are pushed to the left-hand side. This results in the reduction of the amount of CO₃^2- present in the system, increasing the ratio of HCO₃^- to CO₃^2- which intern decreases the pH. Additionally various organisms utilise the anionic species involved in the buffering of the water. The species is just removed from the buffering system, which can decrease of increase the pH depending on which species is removed. But the important fact is that the species has been removed from the species reducing the alkalinity.

How can alkalinity be maintained?

In order to maintain the sufficient levels of alkalinity it is necessary to add more of the anions involved in the buffering system to the aquarium. Furthermore the anions have to be added in the correct ratio otherwise, as pointed out earlier, the pH of the seawater will not tend to the correct value. The sources of these anions are as follows:

The Atmosphere

Carbon dioxide, CO₂, from the atmosphere dissolves into the water and then reacts with water to form H₂CO₃ as shown in (2) above. It must be noted that this does in fact decrease the pH by generating H⁺ in reaction (3) and increase the ratio of HCO₃^- to CO₃^2-. Therefore have to add the anions to the system, by-passing the first two reactions, (1) and (2), in order to attain the correct pH and alkalinity combination.

Carbon Reactors

Works the same as for the atmosphere just more CO₂ can be dissolved in the water by operating under elevated pressures. Also don't have to rely on slower diffusion process from the air over the system into the water.

Water Changes

These introduce the buffer species into the system with the new water, whether synthetic or natural. The species should be in the correct ratio, depending on the type and quality, helping to maintain the correct species ratios.

Powdered Buffers

These are powders containing the important buffering anions such as CO₃^2-, HCO₃^- and the other minor components in the correct species ratios.

Two Part Solution Buffers

These are the new ones on the market and operate in the same way as the powder buffers. But instead of being a powder, they consist of two aqueous solutions: one part that contains calcium plus other important metal cations, and the other with the important alkalinity anions. These are superior to the powdered buffers as solubility of species such as CaCO3, calcium carbonate, is no longer an issue as the Ca²⁺ and CO₃^2- is separated into the two solutions. A counter ion for each ion is then used that generates a species with a much higher solubility, such as calcium chloride (CaCl₂). As a result much more can be dosed from a smaller dosing volume, and all the species are added in the correct ratio.

Calcium Reactors

These not only help maintain the calcium levels as the name implies, but also the alkalinity. They operate as follows, CO₂ is dissolved into the water lowering the pH. At a pH below 7.0 the solubility of CaCO₃ increases, therefore the Ca²⁺ and CO₃^2- are dissolved into the water. As the CO₃^2- anions are added, then the pH range of the reef aquarium should be higher than that of one that uses other techniques. This results from the fact that CO₃^2- is added directly, decreasing the HCO₃^2- to CO₃^2- ratio. They are a superior way of increasing the alkalinity as they operate continuous and add calcium at the same time, killing two birds with the one stone.

Bibliography:
Delbeek J.C., and Sprung J., The reef aquarium: a comprehensive guide to the identification and care of tropical marine invertebrates, vol. 1, Richordea:Coconut Grove, 1995.
Horne R.A., Marine chemistry: the structure of water and the chemistry of the hydrosphere, Wiley-Interscience:Sydney, 1969.
Raven P.H., and Johnson G.B., Biology, 2nd ed., Times Mirror/Morsby College:St. Louis, 1989.

You Wouldn't Believe It!

..... a new thing had popped out of the rock. It is a type of cucumber, similar to the sea apples, with tentacles that are constantly raised into the water column to collect food particles. This guy though is only 20mm long. Since he has lasted this long then he must be finding stuff to survive.

Bereavement Notices

Chromis viridis, Green Chromis
This guy just up and disappeared, all the school has been healthy and active. I suspect that he became a meal for a mantis shrimp or a crab, and don't think it was to health problems. Well, good news, I have just found this chap. He was having bit of a holiday in the overflow, damn fish ;-).

Tridacna maxima, Maxima Clam
Unsure on this loss aswell. Over the first couple of days he was introduced into the Park he opened up more and more each day. Then on about the four day this reversed, and within another 4 days nothing was left. There were no worms, snails or shrimps seen feeding on the clam, even when it was in trouble. I suspect that it's foot was somewhow damaged, and once that happens you can really kiss a clam goodbye. This is a loss that I really felt, both emotionally and in the hip pocket, it was such a nice clam and was only a baby.

Lysmata delbius, Fire Shrimp
I suspect that I lost this one as he molted while in the breeding trap with the other shrimp. As a result he was vunerable and was attached. Now I know not to put two fire shrimp in a confind space together, as they were not like the cleaner shrimp hanging out together without any hassles.

Linckia sp., Spotted Linckia Starfish
Just after the live sand was added to OZ REEF this starfish appeared to get deflatted. From then on he did not recover all and over the space of two weeks just wasted away. It was very sad to watch :-(. What I suspect happened was that the water-vascular system was shocked in some way when the sand was added. And this damage could not be repaired.

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