Thiel Book - Chapter 4

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THE MARINE FISH AND INVERT REEF AQUARIUM
Albert J. Thiel

4.9.2 AUTOMATED DIFFUSION OF CARBON DIOXIDE:

The only difference between a manual carbon dioxide diffusion system, and an automated one, is the fact that you need to add two components to the setup: a pH controller, and an electrode (and a solenoid if you have not done so under the manual setup).

The components that you require to set an automated system up comprise: a carbon dioxide canister, a set of gauges with pressure reducer, a solenoid/magnetic valve, carbon dioxide resistant hose, two CO2 check valves, a CO2 diffuser or, better, a CO2 reactor, a pH controller with a two digit past the decimal point readout, a good quality electrode (see earlier remarks about electrodes), pH calibrating solutions pH 7.00 and pH 9.00, pH electrode cleaning solution, pH electrode storing solution (optional but recommended), and a carbonate hardness test that measures dKH or meq/l (milliequivalents per liter).

The principle relied on is the fact that carbon dioxide lowers the pH. We can thus influence the pH by means of a controller, and stabilize the pH at the value that we determine to be right for our tank. Usually, a pH of 8.0 to 8.2 is suggested, depending on what hardness you maintain your water at. The higher the hardness, the higher the setting. For example if your hardness is more than dKH 15, set the controller for pH 8.2, if it lower, set the controller for pH 8.1.

What happens when you now add carbon dioxide is as follows:

After you have installed the pH controller, by following the manufacturer's instructions, and taken a dKH test to ensure that it is at least 12, set the controller's set point for a pH of either 8.1 or 8.2. Again, follow the directions that came with the unit to do so.
Set up the CO2 system in the same manner as described earlier in the manual section. The only difference is that the solenoid valve is now plugged into the pH controller, and the controller is plugged into an outlet.
Open the canister and start adding the carbon dioxide. The pH will be lowered because the carbon dioxide forms carbonic acid when in contact with water. As the electrode senses that the pH is going down, it will close the solenoid when the pH falls below the set point. The reason for this is simple: it is the function of a controller to ensure that such is what happens.
When the pH now goes up again, because of the hardness of the water, and the good water quality obtained by using a trickle filter, the controller will sense that the pH is above the set point, and reopen the solenoid, pushing more carbon dioxide into the water, and lowering the pH as a result. This, in turn, will prompt the controller to close the solenoid again, as soon as the pH goes below the set point. Because this process is continuous, you have, in fact, stabilized the pH around the set point value. Such is exactly what we wanted to do. CO2 is now being added and the pH is stable.

We already indicated that one of the benefits of adding carbon dioxide is that it enhances the formation of calcium carbonate in the tank. This is a very positive side effect, as all corals need calcium carbonate for growth, and so do calcareous and crustose algae, the pink, reddish and purplish types that so often grow on rocks in reef tanks where the water quality is really good.

4.10 DOSING PUMPS:

Hobbyists use a number of additives to improve the water quality of their reef tanks. These include: vitamins, trace elements, KH generators, iodine and strontium molybdenum supplements, and so on.

Because we have already indicated several times that stability of the water quality is a most important aim to strive for, it does not seem to make much sense to add all these supplements in large doses once a week or so. It would be much better for the water quality stability to add them evenly throughout the day and night. Such a system would only add a small amount of these supplements, but would do so all the time, keeping their concentration just about the same at all times.

Several types of special pumps are offered to do so: dosing pumps with diaphragm mechanisms, peristaltic pumps, gear pumps, etc. All achieve the same result. Cost and minimum quantity of fluid delivered per day should be your guiding criteria when selecting a dosing pump for your system.

Dosing pumps with peristaltic motors typically deliver the smallest amounts of fluid over any given period, especially if they allow the use of several types of internal diameter tubing. Indeed, the smaller the internal diameter of the tubing used, the smaller the amount of fluid dispensed per revolution will be. No 13 tubing, also called spaghetti tubing by some, can be used on several such pumps. The better ones, but also the pricier ones, are made by Masterflex, a division of Cole Parmer, Chicago Ill. Many other excellent brands are available.

Thiel*Aqua*Tech sells a small, very quiet and very reliable, peristaltic pump that delivers about 500 ml per day (slightly less than 16 fluid oz), and should be run on a timer, if the need to dispense even less fluid should arise in your tank. Use a timer that has multiple on/off settings, and set if for one cycle on, and then one cycle off. In that fashion you will be delivering about 8 oz per 24 hours. If you need less still, set if for one cycle on and two cycles off, and you will be delivering about 5.3 ounces per day. Timers with either 15 or 20 minute cycles are to be preferred.

An alternative way of using such a pump, recommended by some authors, is to run the pump only during the day and not after the lights have gone off. In such a case you would be setting your timer on a twelve or so hour cycle (use the same number of hours as your lights are on). The reason usually given is that when the lights are out, and metabolism is low, not as many nutrients etc. are used and dispensing them is therefore not as necessary. The amount of water and nutrients that you will want to add should be selected in such a way that it makes up for evaporated water as well. In doing so, the peristaltic pump performs two functions: it is an automated water makeup system, and at the same time it dispenses all the additives that you normally add to the tank evenly throughout the day (and night).

The question is often asked how the mixture dispensed by a dosing pump should be prepared, and how one can easily determine the quantities of the various elements and additives used that need to be mixed in. Here is a suggested way:

First determine how many ounces of liquid you wish to add to the tank per day. This will vary in every tank. It is dependent on the amount of evaporation, and on the size of the aquarium. If you do not know what that amount is, determine so over the course of a few days by keeping tabs of how much water you need to add, each day, to bring the level of water in the sump of the trickle filter, or in the tank, back to where it normally is.
Let us assume for the purpose of this example that this amount is 16 fluid oz. per day.
Next select a container that will be used to prepare the mixture in.

When doing so, keep in mind that the container should hold several days of replacement water, but not too much either. For example, a one gallon container will hold 128 / 16 = 8 days of supply of replacement water. A 2 gallon container would hold 16 days. Anywhere from 8 to 12 days seems like an appropriate length of time. We select a container that can hold 1-1/2 gallons (such plastic containers can easily be obtained from stores that sell kitchen supplies etc.).

Fill the container with slightly less than 1-1/2 gallons of distilled, reverse osmosis, or deionized water. Note that the water must be distilled, reverse osmosis, or deionized. Do not use regular tap water. It contains too many impurities that can react with the additives you will be using, and can affect them negatively.
In our example, the container we used holds a 12 day supply of replacement water.
The next step is to write down the additive you use, and calculate how much of them you use every day. This means that if you use them only once a week, you must divide the quantity added weekly by seven (etc.)
Again, in our example we assume that we use the following supplements:

trace elements 12 drops per day
vitamins 20 drops per day
KSM 120 drops per day
Iodine 8 drops per day
KH generator 100 drops per day
Kalkwasser 100 drops per day

If the above quantities are used in one 24 hour period, and if the container we have decided to use, holds a 12 day supply of water that will be dispensed evenly throughout those 12 days, adding 12 times the amount of supplements to that water, will at the same time result in all the elements and additives being dispensed in the tank evenly over the next 12 days.
The next step is, therefore, to make up the mixture that the peristaltic pump will dispense so that it contains 12 times (in our example anyway) the amount of nutrients that we normally dispense every day. This means 144 drops of trace elements, 240 drops of vitamins, etc. (use your own figures to determine the required amounts to be added for your situation. The ones used here are just for illustrative purposes).
Next, mix all this in with the water in the container (if you have too much water remove some first), and switch the peristaltic pump on, with or without a timer, to adjust the daily output to 16 ounces.
Your automatic top-off and additive dispensing system is now set up.
Replenish the water and additives in the container as required. If the amount you calculated the first time does not check out, make the necessary adjustments by recalculating all the numbers if need be.

Important remark: Peristaltic pumps use small diameter tubing to transport water from the storage container to, in our case, the aquarium or trickle filter. Because of the manner in which peristaltic pumps operate, that tubing is being compressed constantly, hour after hour, day after day.

Such tubing has a rated life that is normally in the vicinity of 1000 to 1500 hours of usage. If you are running your pump 24 hours a day, you will have to replace it about every 45 to 50 days. If you do not, the efficiency of the pump will diminish, as the inside of the tubing will stick and transport less fluid. Possibly the tubing will burst, and some of the fluid that it is pumping may damage the motor or peristaltic mechanism. Make it a habit to change the tubing before you experience any problems. Write the date you installed the tubing in your aquarium diary, or on a small piece of tape stuck to the pump itself. Use good quality tubing. Tygon, or better still Pharmed special number 13 tubing for peristaltic motors, should be used.

Dosing pumps are very easy to set up and require little or no maintenance, except for changing the tubing from time to time. Make sure that whomever you buy your pump from, can also supply you with replacement tubing, or know an alternative source to obtain it. Check scientific supply house catalogues too. Peristaltic pump tubing can be expensive. Buy from the right source!

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