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The ZEOvit System:
A New Concept in Reefkeeping

By Alexander Girz

Translated by Gary Madl

(This article was originally written in German by Alexander Girz and translated into English by Gary Madl. The translation was done to best represent the original text. Unit conversions are approximate and were applied for easier reading and may not represent the exact amounts.)

In this article, I would like to share my experience in keeping SPS (Small Polyped Stony) corals. The tank described was established in September 2001 and has been successfully operated with the ZEOvit system (by since November 2001. Both the tank and the equipment have primarily been designed to keep SPS corals.

Let me start with some relevant data about the setup:

Dimensions and volume: 220 cm long x 80 cm deep x 60cm high (approx. 86.5” x 31.5” x 23.5”), 1056 liters (approx. 279 gallons), plus 250 liter sump (approx. 66 gal).

Rock display: The reef structure is built exclusively with approximately 100 kg (approx. 220 lbs.) of freshly imported Indonesian live rock.

Lighting: AquaConnect PowerRiga strip light with three E40 socket metal halide bulbs (BLV 10,000 Kelvin, 250 Watt) as well as four blue fluorescent bulbs (ATI Blue plus 80 Watt). The metal halide bulbs are replaced every 6-7 months. Lighting schedule: metal halide 7 hours – fluorescents 12 hours.

Filtration: An external sump is located in a separate room. It is fed by a surface overflow from the main tank. The water turn over between the tank and the sump is approximately 2500 liters per hour (660 gph). An externally powered skimmer (H & S A200-2x1060) with a flow rate of 2000 liters per hour (528 gph) is connected to the sump. ZEOvit filter material in a ZEOvit filter is set with a flow of approximately 2000 l/hr (528 gph).

Water movement: 3 Tunze Turbelle Electronic pumps with 4000 liters (1056 gal) each and 1 Tunze Turbelle Stream pump with 12000 liters (3170 gal) are operated with a multi-controller in pulse mode. Total flow in the tank is approximately 26000 liters per hour (6868 gph). There is a spray bar integrated in the back of the tank to prevent detritus from settling under the reef structure (constant flow).

Partial water changes: 6.25 percent weekly with Reverse Osmosis water.

Calcium addition, trace elements and other supplementation: Schuran Jetstream I, CO2 Calcium reactor in continuous operation (filled with coarse coral sand and GroTech Mg Pro Granulate), Potassium iodide/fluoride, Iron, Amino acid, ZEObak (bacteria solution), ZEOfood 7 (bacteria food), ZEOspur 2 and ZEOstart. About 3 teaspoons of Ca chloride are added every week to keep the Ca level.

Stocking:  95% of the corals in the system are SPS (Acropora, Stylophora, Pocillopora, Anacropora and Montipora); 5% other sessile invertebrates (Xenia, Sarcophyton, Tridacna and Goniopora). There are 30 small to medium sized fish.

Some pictures of the Author's reef tank, which employs the ZEOvit system as part of the filtration.

First, I would like to explain the ZEOvit method and define all of it’s components in order to avoid any misunderstandings.

The following components are manufactured by

  1. ZEOvit (Mix of Zeoliths)

  2. ZEObak (bacterial additive)

  3. ZEOfood (food for bacteria)

The following requirements are also necessary for the ZEOvit method to be successful:

  1.  Sufficient lighting

  2.  Constant use of activated carbon

  3. Optimization of nutrient addition

  4. Addition of elements at low levels

The goal to be achieved:

The purpose of the system is to create a low nutrient environment. Not only are we trying to reduce the measurable levels of Nitrate (NO3) and Phosphate (PO4), we are also lowering the levels of mineral concentrations like Calcium (Ca), Magnesium (Mg) and Carbonate Hardness, (KH) while keeping the addition of trace elements to a minimum.

In the following section, I will address each component of the ZEOvit system and give a brief description and add my own experiences:  

ZEOvit (Mix of Zeoliths)

Zeoliths are a group of naturally-occurring minerals that exist worldwide. Their chemical composition can vary greatly and therefore exhibit different properties of adsorption, ion exchange or molecular retention. Today’s modern industrial applications require very specific properties and therefore, most of the Zeoliths used are either modified natural zeoliths or completely synthetically manufactured.


The ZEOvit proprietary mix of zeolites as supplied by Korallen-Sucht’s mix of Zeoliths consists of four different Zeoliths chosen because of their ability to reduce certain toxins in a balanced way. The useful life of the mix is limited and it has to be exchanged every 6-10 weeks depending on the tanks bio-load. The exchange itself can be done in a single session.

Water flow through the filter material should be active and strong. The amount of Zeolit material used is 1 liter per 400 liters of water. It is important not to exceed the recommended amount. This could have a negative effect on SPS corals and excessive overdose could lead to tissue necrosis and therefore, coral death.

I use approximately 3 liters of filter material for my system. It is rinsed well in fresh water before use in order to flush out fine particles created by abrasion during transportation. An initial cloudiness in the water during introduction of new material is not harmful to any living organism in the tank and usually disappears within one hour. In the beginning, I employed the material in my external sump in mesh bags. The bags were laid out on light diffusers with the dimensions of approximately 20cm x 50cm. The entire area had a flow of about 2500 liters per hour.


Typical ZEOvit "reactors"  Photos courtesy of CaptiveOceans

In January 2003, I modified the way I use the filter material. This change had a very positive effect on the corals. The material was taken from the sump into a ZEOvit filter equipped with an Aquabee 2000 l/hr pump. The filter was placed directly into the sump. Within just a few days, I observed a change in corals placed in areas with lower light intensities. The coral tissue brightened and colors became more intense. The change allowed for more contact time of the water with the filter material.

Several months ago I started to clean and mix the filter material on a daily basis with the help of the integrated mechanism in the filter. This is done during the dark period by raising and lowering a rod about 15 times. The resulting mulm mixes with the tank water. A few weeks later there was a color change and more intensity in some corals. The brownish color of the shaded part of corals was replaced by their natural color. Other corals displayed colors unseen until then. However, the base color of the corals darkens because of this daily cleaning of the material.  

Some of the corals maintained with the aid of ZEOvit.

I would like to emphasize again at this point not to use any other Zeoliths. There are virtually hundreds of different materials with this name. Each and every one has its specific use and was designed or modified for it. Using a zeolith with the wrong properties could damage or destroy all of your reef creatures!

Bacteria (ZEObak)

This liquid solution contains several bacterial strains. It should be dosed for a period of 10-14 days after every exchange of Zeoliths. I primarily follow the recommend dose of 1-2 drops per 100 liters (26 gallons) of tank water. My experience has shown that frequent excessive dosing can lead to tissue loss in certain types of Acropora. Acropora turmida seems to be especially vulnerable. I assume that these types of bacteria have the properties to convert nitrite (NO2), nitrate (NO3) and phosphate (PO4) in a form where it can be skimmed by the protein skimmer and therefore be removed from the system. This is the reason why I sometimes dose this solution outside of the recommendation. The result can be seen in the increased concentrated adsorbent in the protein skimmer the days following.

Bacteria Food (ZEOfood 7)

This substance is also delivered in liquid form and dosed in combination with the bacteria. The recommended dose is 1-2 drops per 100 liters (26 gallons) of tank water. When used with fresh Zeoliths, dosing is done daily together with the bacteria for a period of a few days. After that dosing, a few drops are administered every 4-7 days based on my observations. The manufacturer of this product states that this food has a positive effect on reproduction of the dosed bacteria. In addition, this supplement contains various elements that aid in reduction of nitrate via skimming. It also provides compounds beneficial for growth and color enhancement in SPS corals in a nutrient poor environment. However, success can only be achieved if the above-mentioned conditions and parameters are met.

The manufacturer, , recently improved this supplement so that even with higher dosing, SPS tissue will not darken noticeably. This is in direct correlation with the density of zooxanthellae in coral tissue. Currently, the manufacturer markets this product as ZEOfood-7.

In summary, with the use of the three mentioned elements, it is possible to reach near-natural levels of compounds measurable by aquarists. However, near natural water conditions are not enough to achieve the desired growth rates as well as promotion of intense colors. Some secondary conditions are also required which will be described below.

Heavy Skimming

As mentioned earlier, the basis of this method relies on export of harmful substances through skimming. With this in mind, it is virtually impossible to choose a skimmer that is too large. Continuous use and frequent cleaning should be done in order to keep the skimmer performing at its maximum level. I achieved better results when the skimmer was adjusted to not produce too much concentrated skimmate. The manufacturer recommends not using ozone or UV sterilizers so that bacteria and elements added to the system are not destroyed. This makes sense to me, and for that reason I do not use any of these devices.

Sufficient Lighting

When building the reef structure, I made sure to erect a “reef pile” right below each of the three metal halides. These “reef piles” reach to about 15 - 20 cm (6 – 8 inches) below the water surface directly below the 250 W HQI bulbs. Doing this created areas of high intensity lighting providing optimum conditions for SPS that originated from shallow water areas. I observed that fragments placed in the middle of the tank displayed less intense colors than the mother colonies at the top of the tank. Both the intensity, as well as the light spectrum play an important role in coloring of the corals.

Continuous Use of Activated Carbon

Exceptionally positive results are achieved by continuously using high-quality activated carbon for filtering. The company recommends continuous use of 1 liter of activated carbon per 1000 liters (264 gallons) in the sump. I use 1 liter of activated carbon that is exchanged every 30 days. It is important to keep an eye on the quality of the carbon in order to avoid introduction of harmful substances that can accumulate in the tank over time. It is possible to maintain crystal clear water, which assures unobstructed light intensity and spectrum from the light source. It is beneficial to knead the carbon every couple of days. This prevents channels from forming and exposure of new surface areas for the water to reach. I question the use of activated carbon in a closed canister filter since it also removes beneficial elements. Carbon containing PO4 should never be used. Test the carbon by placing it in reverse osmosis water for a period of 1 hour. Pour the water through a coffee filter and measure the level of PO4 in the water sample. Allowing the carbon to sit in RO water for 1-2 days can also reduce the release of PO4 by carbon.

Optimization of Nutrient Introduction

Keeping with the goal of the system to reach a low nutrient environment, it is necessary to limit introduction of nutrients with top-off water, and to keep feeding to a minimum. There are several ways to do this. I decided on removal of dissolved solids by means of a reverse osmosis system for water changes and top off water since this was the easiest way for me. I added a deionization unit after the RO unit. Another source of nutrients comes from fishes. Their fecal matter, as well as uneaten food adds to accumulation of nutrients in the water. I feed small portions with the pumps turned off to avoid food from drifting into the decoration. This limits the resulting decomposition process of nitrite (NO2), nitrate (NO3), and phosphate (PO4). The amount and type of fishes should be adapted to the type and size of the system.

Addition of Elements in Small Amounts


An assortment of additives and supplements intended for use with the ZEOvit system  Photo Courtesy of CaptiveCceans

Low nutrients, of course, also apply to the addition of elements. I advise against high amounts of additives in this environment, since problems will occur sooner or later. I attribute these problems to the slow but steady accumulation of unused substances. In this case, less is often more. Many of the added elements have toxic effects on the animals if they reach certain levels. Therefore, they bring more disadvantage than advantage. This is the point that requires some kind of change in the train-of-thought with this system. Regular addition of elements in very small amounts and scheduled water changes are enough to avoid deficiencies in the corals. It is impossible to recommend specific amounts since every tank is different. Differences in equipment and stocking of the tank lead to a high degree of individuality. The observation skills of the person taking care of the corals are very important. One must keep in mind that additions in this environment have delayed reactions of 2-3 days.

This fact is very important when adding anything to the tank. Here is the technique I use if I dose an element of which I do not know the reaction. <Editors' note: We always advise that you test for any additive that you wish to use!>  I carefully dose once and wait a few days to observe how SPS corals react. A very helpful indicator is coral coloration. The coral tissue should be light and colors should be intense. Provided that measurable parameters of nitrate (NO3) and phosphate (PO4) are consistently at low levels, any darkening of tissues and disappearance of coloring is always an indication of over dose. In my opinion, this is a much better indicator than the questionable results of many test kits. Sometimes the visual observation can lead to great differences in concentration readings due to the subjective interferences required in these test kits.

As long as parasites are not an issue, subdued colors and dark or brown tissue is in most cases are the result of high nutrients. It can be assumed that either nitrate (NO3) or phosphate (PO4) is present or too many other elements are available.

Furthermore, I have learned from my own experience that constant and daily dosing of elements can have negative effects on coral coloring. I do not have a factual explanation, but I assume that this reduced color intensity stems from constant availability of certain elements. My dosing regimen of different elements is conducted on an alternating weekly basis on a non-regular schedule.

Currently I dose the following elements:

  • ZEOpur2                            10 - 11 ml every 14 days

  • KI/KF concentrate            10-20 drops weekly

  • Iron concentrate                 10-15 drops weekly

  • Amino acid concentrate    10-20 drops weekly

  • ZEOstart concentrate         5ml twice a week

The above-mentioned amounts depend on the SPS colors and may vary.

The following are some reactions that can be observed in my tank when the above-mentioned elements are added.

Trace Elements Concentrate (ZEOspur 2)

This is a new product, which has only been on the market for a short period of time. I have been using it in my tank for 9 months. Its affect can be seen 1-2 days after addition to the tank. The coral tissue brightens up and brown color is reduced, making the natural coral color more apparent. This is the result of a reduced amount of zooxanthellae, and therefore produces better display of the corals’ natural color. The first addition led to slightly reduced colors but adjusted itself fairly quickly. I was able to observe a constant color improvement after each addition. This gain in color seems to have established itself at its peak. ZEOspur 2 has to be dosed exactly as recommended. That means 1 ml per 100 liters (26 gallons) should be dosed all at once every 10 - 14 days. I would absolutely recommend not to over dose this supplement. It is also important to dose the entire amount at once. Reducing the amount and dosing the sum over two days will not work. It takes a bit of experimenting in the beginning to figure out the correct dosing quantity for each individual tank. I would not recommend dosing more than 20% over the recommended amount. I suggest to increase the quantity by 10% dosed a few days later if the recommended amount is without effect. The recommendation is based on the total net volume of the tank including sump, etc.

Potassium Iodide Concentrate

I have noticed that the addition of this supplement leads to improved blue colors in SPS. In contrast to PVP iodide or Lugol's Iodide solution, there is no tissue darkening as long as the amount is appropriate. Another positive effect can be seen in Xenia, with better growth and faster pulsing frequency.

Iron Concentrate

The addition of iron primarily affects the green color formation. This element has to be treated with some caution. Iron is known to promote the growth of algae as well. You can see the same result in the density of zooxanthellae in coral tissue. Darkening of tissue suggests that too much iron is being added.

Amino Acid Concentrate

My observations have shown that the availability of different amino acids primarily aids in growth, as well as coloring of red and pink SPS. I have also noticed better polyp expansion. Too much addition will lead to darkening coral tissue.


The manufacturer states that this concentrate serves as a food source for certain bacteria cultures responsible for breakdown of nitrate and phosphate. Within just a few days of first introducing this solution, I noticed that SPS tissue started to become lighter. This condition was maintained with the addition of this concentrate. Colors in SPS corals became more intense. The addition also seemed to have a positive effect in the yellow colored Acroporas. I attribute this to reduced phosphate and nitrate levels, which leads to reduced density of zooxanthellae. It is unclear if SPS corals utilize any elements of this supplement. Furthermore, as mentioned earlier, I also add infrequently bacteria food, which contains other elements, such as vitamins. In my own observations, this also has shown positive effects on coral colors.

I hope I was able to convey a certain sense for each of the individual elements. The difference between positive and negative effects is very narrow and is up to the user to adjust the amounts based on their own observations for their own system. Sometimes the mistake is made that elements are added if colors get lighter. Many times the opposite would be the correct measure to optimize colors.

I do not add strontium to my system, since I have not been able to see any advantages. If strontium is available, this element will be used in SPS corals to build its skeleton just like calcium. High amounts of strontium can lead to less stable and, therefore, more brittle skeletons.

Parallel to a low nutrient environment, you will also have to adjust calcium (Ca), magnesium (Mg) and carbonate hardness (KH) to natural levels. The following concentrations have shown to work for me:

  • Ca              420       460mg

  • Mg           1290       1350mg

  • KH                7        8

  • Salinity       33        34 ppt

Higher concentrations show no advantage. Neither growth nor coloring in SPS corals can be positively affected. However, if any of the mentioned parameters deviates too far, the result can quickly become negative in the established environment. If you compare these concentrations with the average values of reefs in nature, you will notice that conditions are very similar. I have also observed that these values have to remain as stable as possible in this low nutrient environment.

If corals show tissue recession, many times the reason can be found in the above-mentioned parameters. After bringing levels back to normal, tissue loss usually stops within a few days.

In summary, it is important to reach a balanced state in the above-mentioned parameters. If one of the parameters fluctuates too much, it will have a noticeable negative affect on the SPS coral. The best control parameter next to available water tests is the ability of the observer to notice changes. At this point, I would like to offer my advice regarding exaggerated responses to “measurable” problems. Many times it is a test error or the result of expired or inappropriately-stored test kits. If I notice that one of the parameters is noticeably off, I test the result again,usually with a new test kit- before I start any measures. If the original test result proves to be correct, I slowly implement the appropriate steps to account for the deviation during the next few days. 

Special care must be taken with the reading of your salinity. I was able to use three different test methods (specific gravity meter, refractometer and conductivity meter) for 5 individual tests. I noticed significant deviations. The test results varied from 1.021 to 1.026. Starting at a salinity of 1.0255 (specific gravity) many Seriatopora and Stylophora can be very sensitive and may show a definite tissue and color loss. Reduced color intensity, as well as slower growth can be seen in all SPS corals at this salinity level

Depending on the age of the system and the current nutrient levels, it can take up to 6 months for this system to show results. After that, however, success should show fairly quickly and conditions can be maintained if the above-mentioned steps are followed.

My experience with this method has shown that SPS corals are more sensitive to calcium and magnesium deficiencies in this low nutrient environment. Each of the values should be in the above-mentioned range. I also want to annotate that the test kit readings are often very different and wrong. If I use a new test kit, I first check it with natural seawater that I collected from a coral import. Also, the salinity level is important. A low salinity level is more tolerable than high salinity. An indication of deviation of these parameters is the slow but steady tissue recession on the base of the SPS coral. If this is the case, the parameters should be properly checked and adjusted if necessary.

In my opinion, patience, care, observation, and the ability of reserved addition of elements next to the “common” technical equipment are necessary to get the desired results with this method.


Zeovit Reactor   12/8/06
Hi Bob,
<Hey Ramy, JustinN with you today.>
I have read all the articles on wetweb regarding the ZEOvit reactor. One of my local fish dealers has already installed one to his display of SPS and to tell the truth, the corals look very healthy, very impressing colours and super polyp extension. I need your thoughts about it, I have just recycled my tank and planning to keep SPS .I know it will be lots of work but if it is worth the effort, why not ? Thank you.
Toronto, Canada
<Well, Ramy, I don't have any personal experience with the Zeovit system, however I too have read a great deal about it. It certainly can be successful, and can have some beautiful results, however the same can be achieved through a dearth of methods. There are no absolutes in this hobby, and a lot of times the main point is to find what works best in your setup. What I understood about the Zeovit system led me to feel there was very little margin of error in the system, requiring the constant checking of levels and maintenance of filtration aspects. That said, if you are willing to put the work involved in, the results certainly can be worth it. Its entirely subjective! Hope this helps you! -JustinN>    

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