On this page, we would like to continue our discussion on different types of chemicals encountered in maintaining saltwater aquarium. The two major topics that we want to discuss are Reverse Osmosis and Ozonization. To begin with our discussion, let us look at the source for all of our saltwater aquarium water - tap water.

Table of Content

Reverse Osmosis
The General Principle of a Reverse Osmosis Device
A Simple Reverse Osmosis Device
A Better Reverse Osmosis Device
Silicate, Phosphate, and Nitrate
Test Strips
A Brief Summary
Chemicals that you should constantly monitor
Iodine and Potential Drawback of Reverse Osmosis
Activated Carbon vs Ozonizer
Special Note

Reverse Osmosis


Regardless of the size of your tank, all of us use the tap water to mix with the salt to produce the saltwater for our tanks. Unfortunately, the tap water that comes straight from our pipe does not necessary be perfect for our saltwater aqaurium to use. The natural sea water does not contain as much minerals as the tap water connected to our house. The natural sea water is oligotrophic, which means that the natural sea water is not rich in nutrients.

Reverse Osmosis is meant to remove the harmful chemicals that are present in the saltwater aquariums. These harmful chemicals are phosphate, silicate, and nitrate. The first two chemicals, phosphate and silicate, are usually present in tap water. The nitrate, however, is produced in the biogogical decomposition of the nitrogeneous cycle. It is the end product of the nitrification, the second stage of the denitrification process. Remember that the nitrification process is to turn ammonia and ammonium to nitrite and nitrate, so that the nitrogeneous compounds can be further dissimilated.

In the extensive discussion of protein skimmers, we have learnt that the break-down of the nitrogeneous organics are partly taken care of by the living organisms inside the tank. However, since the rate of producing the organics is usually much faster than the rate of breaking down the organics, it is necessary to have a protein skimmer installed in all saltwater aquariums. The job of a protein skimmer is to remove the organics before they have been properly broken down. This, in essence, the amount of organics for the biological load in your tank to handle. The purpose of using a Reverse Osmosis device is similar in that it is to remove the phosphate, silicate, and nitrate before an excessive level is reached inside the tank.

In fact, a Reverse Osmosis device is a lot more powerful than we just described. It should be considered as the first safety guard against problems that may occur in your tank. This is very true if you are living in area where drinking from tap water is problematic, like Europe and U.S. The Reverse Osmosis device is usually connected directly to the water mains, and hence, you should consult with a plumbing consultant before it is installed. The water will first be passed through a pre-filter filled with activated carbon to remove chlorine - commonly added to our tap water in the water treatment plants. The water is then forced through a mechnical filter to remove the large particles from the stream. The key of a Reverse Osmosis device is the membrane that the water is then forced through. The membrane is an unltra-fine grid. The water is passed through the membrane at a pressure that is higher than the osmotic pressure. As a result, the membrane keeps most of the organics and inorganics dissolved in the water before the water enters the sump.

The General Principle of a Reverse Osmosis Device

So what does it mean when the water is passed through the membrane at a pressure higher than the osmotic pressure? Let us review the Osmoregulation that we have discussed in previous pages. Since the saltwater aquarium, where you have just bought your fishes from, is very likely to have a different chemical condition than that of your own tank, the fishes may have to adjust their own bodies to the new condition in your tank. The adjustment is the active transport of the high concentration of chemicals inside the bodies out to the ambient water, or vice versa. The result of the adjustment is to distribute the chemicals evenly among the regions having a different concentration levels of the chemical previously. The chemicals flow from high to low concentration. This is Osmosis, or diffusion.

However, immediately you see that this does not fulfill what we want to achieve. We do not want more phosphate, silicate, nor nitrate inside our tanks. We want to keep them away from our tanks. That is, we must reverse the process of Osmosis. We want to force these chemicals to go from low concentration regions to high concentration regions. Hence, the name of Reverse Osmosis. There is a very helpful analogy to enhance the understanding of the Reverse Osmosis. If you imagine an electric circuit as a waterfall, the stream of electrons (because of gravity) is only going to flow from the a high pressure point (or high voltage) to a low pressure point (or low voltage). To keep a circuit running, there must be a battery to pump the water from the low point to the high point. The Reverse Osmosis device is like a battery in a circuit in that it raises the voltage from a low to a high point.

When do you need a Reverse Osmosis device? The device is required in regions when the tap water is highly mineralized. Chemicals such as nitrate, phosphate, silicate, alumium, copper, zinc are to be removed by the device. Where do the alumium, copper, and zinc come from? They can come from the degrading of your old pipes connecting to your water system. Copper and zinc, and os in the tank. The mineralization, however, produces color substances that give your water a yellow hue. Activated carbon can be used to remove the tinge. However, the problem of using activated carbon is the potential bleaching of corals. Hence, most people prefer the use of an ozonizer instead. Ozonizer had been mentioned a couple of times before when we were discussing the use of Redox devices. Ozone (O3) is a very powerful oxidant. That is, it can be used to break down the nitrogeneous organics into inorganics, or to finish the decomposition process, without releasing any harmful immediate products, like nitrite. Since ozone is toxic, care must be taken when you choose to use the ozonizer. First, you should never connect the ozonizer to the tank directly. (Same as denitrification filter because its effluent is extremely low in oxygen.) Second, you must have a Redox device to monitor and control the ozonizer. The usual set up is to connect the ozonizer to the air in-take of the protein skimmer, so that the ozone gas can be used up as soon as possible.

A Simple Reverse Osmosis Device

Reverse Osmosis Devices are very popular in United States, however, not so popular in Canada. But, the use of such a device is still recommended since the quality of your tap water is a dominating factor in determining how the quality of your tank is going to be. The simple reverse osmosis device is a CORALIFE product, the PURE-FLO device with a celluose triaceate (CTA) membrane.

Here is the CORALIFE PURE-FLO reverse osmosis device. You can think of the entire device as one big filter which takes water from your house's plumbing system (the yellow tube), filters it, and passes through the other two tubes. The blue tube is the purified water and the red tube is the waste water, or highly mineralized water. But remember that the device should not be connected to the sump directly. The red tube should be fed to a drain. The purified water coming out of the blue tube should be collected in a plastic container. Since the purified water does not have much minerals, you can then mix the water with salt and add the amount of electrolytes to fit your own need.

It is recommended in the manual that a clean plastic container should be used instead of a metal container. Inappropriate storage containers can introduce salts and other ions (so make sure that the container is free of any detergent residues) to the purified water.

Before you actually use the solution, do not forget to check the pH and hardness levels. If your tank is having any problem, you can add the medication to the solution as well. You can also check for other chemical levels before you put the water into your sump.
Now let us look at the two components of this device, the sediment pre-filter and the membrane housing. The sediment pre-filter is the top cyliner and the membrane housing is the bottom (and bigger) cylinder. The membrane that comes with this device is a celluose triaceate (CTA) membrane. (There is another type of membrane, which we will mention shortly.) The installation and assembly process are very simple and only component that you need to assemble for a new unit is the membrane. The pre-filter shoould be replaced every 6 months, whereas the membrane should be replaced annually. The replacement, of course, also depends on the water quality of your source water as well. You may need to replace the parts more frequently than recommended. Note that the sediment pre-filter included in this device is only the mechnical filter, but not the carbon filter mentioned in the general principle of a Reverse Osmosis device.

A Better Reverse Osmosis Device

Here is another Reverse Osmosis device from CORALIFE. The principle of this device is almost identical to that with the CTA membrane product. The difference, however, is also quite obvious. It handles a larger volume and it has a second filter besides the sediment pre-filter, the right (vertical) cylinder. The carbon filter is the left (vertical) cylinder. The white cylinder is the membrane housing. The other feature that makes this Reverse Osmosis device better than the one shown above is that this device comes with a thin - film composite (TFC) membrane. The TFC membrane is an inheritally better membrane than the CTA membrane.
The general installation, assembly procedure, and the maintainance details are identical to the CTA membrane. However, there are a few points that you want to keep in mind:

Silicate, Phosphate, and Nitrate

To complete our discussion, we feel that it is better to cover the basic knowledge of a few other chemicals that we did not cover on the More Cheimcals page and to help you appreciate the importance of a Reverse Osmosis device, rather than simply saying "they are harmful and must be removed."

Silicate

Silicate (SiO2) are most commonly encountered in setting up a new marine tank. Silicate is the nutrient of a type of algae called diatoms. Diatoms make use of silicate molecules to construct their cell walls. As a result, excess silicate leads to a bloom of diatoms in the tank. The diatoms are usually not a problem once the biological cycle is established and the other types of algaes dominate the tank. Thus, we see that the diatoms, in fact, are constantly competing with the other algaes, such as the red and brown algaes for the dominant position. Excess silicate that leads to the diatoms dominating in the tank discourages the normal growth of the other good algaes. Remember algaes are good for photosynthesis and partly responsible for the chemical decomposition in the tank.

Phosophate

Phosophate are set free in the decomposition of plants, and other dead micro-organisms. (Remember the nutrient bombs issues.) What may not be commonly known is that there is a pool of phosphate present in the tank at all time. The phosphate molecules are commonly found in water in the form bound to the other chemicals. The interesting point is that the pool of phosphate is inversely related to the pH level in the tank. That is, more phosphate molecules are released if the pH level is low than if the pH level is high. Since phosphate is an essential nutrient to algaes, the release of the phosphate molecules will result in an uncontrolled growth of algaes. This gives another reason for you to monitor your pH level closely. (Fortunately, phosphate molecules can be removed effectively by protein skimming.)

Nitrite and Nitrate

Nitrite (NO2-) and Nitrate (NO3-) are correspondingly the immediate and the end products of the Nitrification process. Nitrification process, if you remember, is the process of turning ammonia and ammonium into nitrite and nitrate and they are also nutrients to algaes. However, nitrite does impose a more serious threat than nitrate in that a high concentration of nitrite inhibits the nitrification process and nitrite poisoning can generate respiratory difficulty for your fishes. This can easily kill your fishes.

Test Strips

As you can see that most of the test kits available are quite complicated and tedious to use. The test kits that you see so far on this page usually has 3 to 5 different chemicals that you must mix with during the test. In fact, you can do better than this! Below is a picture of such a product:


The first four on the left are different test strips for pH, Alkalinity, Nitrate, and Nitrite. The other two are eliminators. The eliminators are to be used when the result of your tests showing that one, or more, of the chemical levels have been exceeding what it should be. To preform the test, all you need to do is to dip the end with chemical on it into the water and hold it for a few seconds and wait for the chemical to turn its color once you have taken it out of the tank. The results are quite accurate and the colors are quite easy to distinguish. If you have used any test kits before, you know that it is sometimes quite difficult to match the color of the test result with the color chart included in the test kit. These test strips have also solved the problem for you. Because of these two advantages, they have become the most popular test kits in our shop!

A Brief Summary

Here, we can summarize the basic problem of having excessive silicate, phosphate, and Nitrate in our tanks. The three chemicals are problematic because they are nutrients to different types of algaes. The excess levels of these chemicals are going to induce a bloom of algaes that are not supposed to dominate the tank. This then screws up the normal cycle in your tank. While phosphate molecules can be removed effectively by protein skimming, the silicate and nitrate can only be removed by Reverse Osmosis.

Chemicals that you should constantly monitor:

Calcium

Calcium is definitely needed for reef tanks. Same as our own bodies, corals need Calcium to build their skeletons for growth. There are many different ways to add calcium to your tank, however. Do you remmeber the Calcium Reactor and Carbon Dioxide Reactor (together with a pH controller) set up discussed on the More Chemical page? That is an advance system that you can install to your tank. While the system offers different advantages to us, it can also be quite expensive! The most common way to add calcium to your tank is to use the chemicals that have been prepared for your own tank. (The CORALIFE product is only shown here as a sample; we do carry other products as well.) The Calcium test kit is similar to those shown below. It comes with a few chemicals that you can mix with the water sample.


Strontium

It has been widely accepted that Strontium is highly essential in the formation of the coral skeletons. The coral skeletons are built of calcium carbonate and also strontium carbonate. There have been questions concerning the real significance of adding Strontium to the tank. You may be able to give away without adding much Strontium to your tank. However, we do use Strontium in our own tanks and test the Strontium levels constantly. So we do advice the use of Strontium in saltwater aquariums.
Vitamin

These three products contain vitamin that you can safely add to the tank. You may consider adding this and the trace elements solution to the plastic container and wait for the solution to be settled.

Iodine and Potential Drawback of Reverse Osmosis

Iodine (I) is necessary for the red and brown algaes to grow. Iodine is also desired because when combined with the other trace elements, a UV protective pigments can be formed. The protective pigments can then provide a guard against bleaching. Here, we can see a potential drawback of using a Reverse Osmosis device: If the pre-filter of the Reverse Osmosis device uses too much of activated carbon, the trace elements can also be greatly reduced by the active carbon. Hence, bleaching of corals results.

Activated Carbon vs Ozonizer

There is indeed another reason for the use of activated carbon. The by-products arise in the decomposition process are essentially nutrients to the algaes or other micro-organisms in the tank. The mineralization, however, produces color substances that give your water a yellow hue. Activated carbon can be used to remove the tinge. However, the problem of using activated carbon is the potential bleaching of corals. Hence, most people prefer the use of an ozonizer instead. Ozonizer had been mentioned a couple of times before when we were discussing the use of Redox devices. Ozone (O3) is a very powerful oxidant. That is, it can be used to break down the nitrogeneous organics into inorganics, or to finish the decomposition process, without releasing any harmful immediate products, like nitrite. Since ozone is toxic, care must be taken when you choose to use the ozonizer. First, you should never connect the ozonizer to the tank directly. (Same as denitrification filter because its effluent is extremely low in oxygen.) Second, you must have a Redox device to monitor and control the ozonizer. The usual set up is to connect the ozonizer to the air in-take of the protein skimmer, so that the ozone gas can be used up as soon as possible.

Special Note

If you are interested in purchasing the Reverse Osmosis device with CTA membrane, we have a good news for you. The device shown above is the last one in our stock. Hence, we are willing to sell it at a special price $ 100 CAN. (Regular price $160 CAN). If you are interested, please contact us. The special offer is available on a first-come-fist-serve basis. Don't miss it!

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