Chemical News.

Introduction

The primary elements consumed by corals and coralline algae need to be replaced at a rate which keeps up with the demand, with the aim that the levels of these elements remains stable. Stability is a key word often used and quite rightly so as in a reef environment the short term levels of elements (short as in decades) remain very constant with the consequence that reef inhabitants have not evolved for rapid changes in water parameters.

The Primary Elements

There will probably be debate between reef keepers for as longs as there are reef keepers about the aspects of the reef environment which are important to the survival and growth of coral inhabitants. For this I am going to limit the list to four which are:

* Calcium
* Carbonates
* Magnesium
* Everything else

The Everything else category is somewhat a catch all, but a valid one as you will see in the detail.

The Ingredients

It would be very nice if we could just take a drop of pure calcium, a drop of carbonate, a drop of magnesium and a drop of everything else and just drop them into the tank. The levels would all be added to and problem solved.

But we can not just do that, the forms that they would take would not make them readily biologically available which is the whole point of doing it, so we need to look at other avenues.

What Hans Balling documented is a way of adding versions which can become biologically available and in combination which can be balanced with the other elements within the environment.

The short list of items to be added becomes:

1. Calcium chloride dihydrate (CaCl2-2H20)
2. Sodium Hydrogen Carbonate (Na HCO3) (aka Sodium bicarbonate Baking Soda)
3. Magnesium Chloride Hexahydrate (MgCl2-6H2O)
4. NaCl free reef salts  your tub of reef crystals without the table salt.

Chuck them in, give it all a stir and there you go.

How to Bake A Cake

Ok, so just chucking them all in and sticking it in the oven probably won’t get you a very nice cake, trust me, been there, lumps of dry flour and baking powder do not do wonders for the taste.

In the same way throwing lots of powders into your tank is not going to endear you to your livestock either. They will probably do the obvious thing and fall over and die. So what we need to do is add them in a way that benefits them rather than kills them.

And at some point explain why we need #4 above.

If you look at #1 and #2 on the list you will find we are adding things we want:

* Calcium
* Carbonates

and things we did not want:

* chloride
* sodium

Now the ones of you who are still awake will notice that chloride and sodium look familiar in combination, SodiumChloride may be one of the few compounds that most people know, its common table salt, and is about 70% of the bucket of reef salts.

So if we do add #1 and #2 we end up with the additional calcium and carbonates which is good, and also more SodiumChloride which we did not want, and so we need to do something about it. We ca not just pull it out of the water, it is not that easy, but what we can do is add everything else from the bucket of reef salt to balance it all up again. So we add #4, the NaCl Free Reef Salts. With that addition we have now added:

* Calcium
* Carbonates
* Reef Salt
* Water

which looks quite a bit better. The only downside now is that we have added lots of salty liquid to the tank, a bit like topping up with mixed water rather than RO water, a mistake often made by beginners.

If you imagine your tank level or sump return level if you have one then the levels will now be higher than when we started. If we ignore evaporation for a moment then eventually your tank will overflow and you will have a wet floor. Thanks Hans! If we put evaporation back into play what will happen is that you will top up with less RO than normal which will increase the salinity of your tank over time.

The solution is simple; just remove as much as you add. Sum up the volumes in #1, #2 and #4 and then just take out that much tank water. It will put the levels back on track letting your top up do its job.

And, simply put, that is the basics of Balling. Add stuff, balance it out, and level it out.

A Chemistry Primer, or How to Weigh an Atom

So where were we, ah yes, we have just taken the cake out of the oven and it looks interesting. A slab of brown cake like stuff, looking good. We cut into it and the whole thing falls apart, and another aspect to cookery becomes apparent: you need to measure your ingredients. Just pouring stuff into the bowl does not work.

So, how much do we use? For that we have to delve a little into chemistry looking at how much stuff weighs so we can weight it out.

The important factor is that we add calcium and carbonate in the same relative quantity that they are consumed. Biologically the consumption is

Ca2++2HCO3 <=> CaCO3 + CO2 + H2O

which means take one atom of Calcium and two molecules of Carbonate which combine to form one molecule of CalciumCarbonate, one molecule of carbon dioxide and one molecule of water. From this we can tell several things:

* That it is the Calcium (Ca) and Bicarbonate (HCO3) that are the inputs
* That two units of Bicarbonate are used for each unit of Calcium
* That carbon dioxide and water are by-products of calcification

So we need to ensure that we add the ingredients in the same proportion, that is two units of Bicarbonate for each unit of Calcium, and that we balance out the resulting NaCl with NaCl-Free salts.

In chemistry most measurements of the amount of a molecule Is done in mol. Each mol of a substance contains the same number of elementary entities (atoms, molecules, etc), and normally it is the gram-mole which is used. A gram-mole is the quantity of a substance whose mass in grams is equal to its formula weight. This makes it quite easy to weight out substances so that they are in the relative quantities we need.

The important bit is working out the formula weight and for that we need to understand a little more about atoms. Each atom has a particular mass and these are well known quantities and appear on a periodic table of elements. The important elements to us for this purpose are:

and the way to determine the molar mass is to add up all of the bits to get the total atomic weight for one entity and then that amount in grams is one mole. Showing this makes it much easier:

Determine the atomic weight of CaCl2 – 2H20 by adding the atomic weights of the parts:

First determine the atomic weight of CaCl2

40.078 + 2×35.453 = 110.984

Then determine the atomic weight of H2O

2×1.00794 + 15.9994 = 18.01528

Then add them together remembering we have two molecules of water

110.984 + 2×18.01528 = 147.01

Determine the atomic weight of NaHCO3:

2.9898 + 1.00794 + 12.0107 + 3×15.9994 = 84.00664

So from this we now know that one mole of CaCl2-2H20 weighs 147.01 grams and one mole of NaHCO3 weighs 84.00664 grams. Thus as we need twice as much of one to the other it is simply a case of weighing out the proportionate amount, which is where Balling gets his often used figures of:

* 147g of CaCl2-2H2O
* 168g of NaHCO3

and he dilutes each of those to 2L of water, which now means that the same quantity of water from each contains proportionally correct amounts of the two ingredients. That dilution is done to a total volume of 2L, not 2L of water plus the ingredients, so the best way is to measure out 1.5L of water, add the chemicals and then top up to 2L by adding more water.

In those two mixes we now are adding those bits we want, and those bits we do not which as we noted before is the Na from the NaHCO3 and the Cl2 from the CaCl2. Fortunately we are adding twice as much NaHCO3 as we are CaCl2 so for each unit of addition we have two units of NaCl resulting. So for each 2L added we are adding two moles of NaCl.

The atomic mass of NaCl is 58.443 which means we are adding 116.89 grams of NaCl for each 2L mix we add. As NaCl represents 70% of the ingredients of marine salts we now have to add the remaining 30% to get to a full marine salt mix. As 70% weighs 116.89 grams it means 100% weighs 167g, meaning that the 30% weighs 50 grams, once again the figure that Balling uses as the third container, a mix of 50g of NaCl-free salts to 2L water.

So we have ended up with three mixes of which we add in the same quantities to ensure a balanced addition that adds Calcium, Carbonate and balanced marine water.

So How Much Do We Add Then?

Quite simply It depends upon your consumption, and for this you may have to guess a little, or if you are currently using other additives you should be able to work it out from the statements on the bottles which often say how much the bottle adds, you can then work out how much you are adding on a daily basis.

If you are not sure then an easy way of working it out is to stop adding anything, settle for a day and then take a Calcium reading on a daily basis at the same time. The difference between them will tell you how much in ppm (aka milligrams per litre) your tank is consuming. This figure is very useful as you end up with how many grams of Calcium you need to add a day and it is very easy to work out from that figure how much of the mix you need to add daily.

Let’s assume you have done the above daily tests and you are losing 5ppm per day of Calcium, and that you are running a 200l tank (figures chosen to be easy). This means that you are losing:

* 5 mg per litre x 200 litres = 1000 milligrams, or more commonly known as 1 gram

We know that our first mix with CaCl2-2H2O has one mole of Ca per 2L, and that one mole of Ca weighs 40.078grams, so we now know that we have to add 1/40.078 moles of Ca a day. That means we have to add 1/40.078 of the 2L mix, which works out at 50ml per day.

There you go, for a 5ppm loss in a 200l tank you have to add 50ml of each mix, and then to balance out the water levels you have to remove 150ml of water from the tank.

You could look at this as simply 5ml of each mix per ppm loss per 100l of total volume. A handy figure meaning that you don’t have to understand any of the above to be able to use the Balling Method. Just multiply up for your loss and for your size tank and use that amount.

And the Magnesium part?

Ah yes, that bit. Using the known figures of relative usage between Calcium and Magnesium on average it can be shown that for each 147g of CaCl2-2H2O we are adding we need to add 34g of MgCl2-6H2O. This can actually be simply added to the same 2L mix as the CaCl2-2H2O.

That figure is actually an average, and the best way of knowing what your tank is consuming is to measure it on a longer term basis and adjust the amount appropriately. For example, if your Mg is sinking relative to a stable Ca then increase the quantity in the mix.

One concern this raises is that we have fortified that mix with more Chloride than we are adding Sodium, and at this point in time this remains unresolved. Further investigation is being conducted as to the resolution of this. Simple solutions such as reducing the quantities of each to result in a balance of Na and Cl will throw out the Ca and HCO3 balance.

Getting it from the Mix into the Tank

So far we now have a number of containers with various mixes of chemicals in them allowing us to add calcium, carbonate and a balancing mix of NaCl-free salts. It would be totally feasible to perform the final step manually by measuring out a set amount on a very frequent basis and adding it too the tank, and then removing a carefully measured amount. The problem with this approach goes back to the quest for stability and easy of use. Building in manual processes should be avoided as they will always end up being put off until later.

So the best approach to take is to setup a means of automatically dosing the mixes and removing the excess tank water. There are a number of different products around which can do this; I use an Aquatronica for other tank automation so it makes sense to use the dosing pumps available for that. For standalone purposes GroTech do a triple dosing station which can be expanded up to eleven channels, which easily will cope with the demands of this process, and for GHL Profilux users a dosing pump is available for that as well.

Each of these devices are programmed in a different way, however they all will allow very small amounts to be added on a frequent basis rather than a small number of high amounts. This spreads the dosing evenly throughout the day keeping the levels stable rather than rising and falling. As the main consumption of Calcium and carbonates will be during the lit hours, the dosing can be restricted to that time.

It is advised to always dose into a location of high flow in order to mix the additive as quickly as possible, but do remember to avoid the situation where the feed line can become a source of siphoning from the tank into the mix containers and onto the floor. It is best to drip the mix in rather than having the feed ending under water.

With all of these devices setting the amount to be dosed is simply a case of entering it into the device, this is the good part with the Balling method, once the pumps are setup increasing the dosing rate is a very quick and easy job.

When looking at the cost of the NaCl-Free salts do remember that they may appear expensive, but you are only buying the expensive parts of the salt and not buying the 70% common table salt part of a standard marine salt.

Conclusion

And that is about it, the darker side on Calcium and Alk addition but well work delving into, as with Balling it is simply a case up dialling up a higher addition if your consumption goes up (indicated by falling levels so keep testing) rather than having to fiddle with flow rates and the pH and alkalinity of effluent from a calcium reactor, or hitting the limits of addition using a Kalk stirrer.

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