ZEOvit® System: Understanding the Basics.

by Christine Lord

I am often asked by fellow aquarists how the ZEOvit® System works and what is needed to run a basic ZEOvit® System. In this article I will explain only the basic components of the ZEOvit® System and how they work together to control nutrients, feed corals, and produce a healthy vibrant reef tank.
The system is not as complex as most people think but it does require the user to acquire some new habits and develop a more observant eye for what is taking place in the aquarium. ZEOvit® is not a plug and playfiltration system and for this reason it simply is not for every hobbyist out there. This said, I truly believe running a ZEOvit® system can make you a better reef aquarist.
In this article I will only be only referring to what is considered the fullZEOvit® System. There are many people running what is referred to as hybridZEOvit® Systems. These hybrid systems run other methods and media such as bio-pellets, nutrient absorbers, algae scrubbers, mud, and other methods to control nutrients but may dose any number of Korallen-Zucht (KZ) ZEOvit® products in conjunction.
The ZEOvit® System seems to be best suited to tanks that keep primarily small polyp stony (SPS) corals however, contrary to what some believe, almost all corals can be kept successfully in a ZEOvit® tank.  One exception may be non-photosynthetic (NPS) corals which require larger quantities of food, more frequent feedings, and lower light. There are always exceptions to rules in this hobby but generally SPS corals and most species of large polyp stony (LPS) corals do quite well in these systems provided proper placement of corals is considered.
A tank that is currently using another nutrient control method can be converted to a full ZEOvit® System but this requires a specific transition process which is beyond the scope of this article. Information and help with conversion can be found online in the ZEOvit® Forum (www.zeovit.com).
Starting and cycling a new tank with the ZEOvit® System is much easier than converting an existing one that has been running using another filtration method. Korallen-Zucht advertises a 14 Day Cycleprogram, detailed on their web site (www.korallen-zucht.de), that will allow you to add fish and non-sensitive corals safely on day 10 of the cycle. I have not done this personally however, I do know this 14 day cycle works well if you follow the guidelines carefully.  
Korallen-Zucht has produced a detailed guide available on their web site that explains all the inner workings of the ZEOvit® System along with detailed information regarding their products. Below, I will briefly explain the basic ZEOvit® System with some reasoning behind how and why it works. I will also share with you some personal experiences with using the system emphasizing critical components and common mistakes made by first time users of the system.
Recommended Requirements
I cant emphasize enough the importance of following the below requirements, they will help insure long term success with the system. There is a reasoning behind everything mentioned below, substituting any part of the KZ recommended frame work for the system will usually result in issues that will only need to be corrected later. I recommend starting off as recommended, this will save you time, frustration, and money down the road, not to mention potential loss of corals and other livestock.
The following is a list of Korallen-Zuchts and my own recommendations required for the system to run stable and properly over time:
Flow: Good flow is necessary for any reef tank regardless of method used. Flow should not be laminar in nature, oscillating and alternating flow patters that cover the entire tank are what corals require for respiration, feeding, excreting waste, and general health. Flow levels that are too high can be counter productive and can even damage coral tissue. Flow levels that are too low will not allow for corals proper exchange of elements, nutrients, and gasses. Low flow will also allow detritus to develop in rock and substrate causing excess dissolved nutrients to occur. It is worth investing in a good controllable circulation system for your tank.
Substrate: KZ recommends a course aragonite gravel 2-4mm grain size that is roughly 1(25.4mm) deep. This would be considered a shallow sand bed. This should not be “live” sand - live sand has been extremely problematic when used in conjunction with the ZEOvit® System. This type and depth of substrate will help keep the system more biologically stable while not allowing for a great deal of detritus build-up. It is still recommended to vacuum the substrate with every water change to remove the natural accumulation of detritus that occurs.
Rock: These days good healthy live rock is hard to find but it is the recommended rock to use with the ZEOvit® System. Dry rock (base rock) is not recommended because it lacks the micro organisms that help keep the natural filtration varied as it is in the natural ocean. While dry rock lacks all the pests organisms that typically come with live rock, its also lacks the beneficial organisms that perform many functions including filtration. Dry rock commonly comes with bound nutrients that leach for months, some times years into the water column causing all sorts of issues. I personally recommend using the best live rock you can find, it is the foundation of your reef tank.
Refugiums: You can use a refugium provided it is only being used as a refuge area for organisms and not part of a filtration method. Macro algae do not fair well in the low nutrient system you create with ZEOvit®. Algae will begin to die and foul the system. I recommend macro algae not be used. In addition substrate should not be more than 1(25.4mm) deep, preferably no substrate should be used in the refugium. This is however, a good place for additional live rock, especially if your display lacks adequate amounts of rock.
UV Sterilizer: A ultra violet (UV) sterilizer should not be used at any time. The ZEOvit® System is a bacterial driven system that produces suspended bacteria. Killing this bacteria is counter productive to the method. (More on this later).
Ozone: Ozone should never be used at any time. Ozone increases the REDOX potential of water making it difficult or even impossible for bacteria to survive.
Lighting: MH, LED, and T5 lighting, or combination of those, will work fine with the ZEOvit® System. There is much debate regarding lighting so I will not go into detail here. KZ and myself prefer T5 lighting mainly because of the diffusion and spectrum offered by this type of light source. SPS corals often grow densely and can overshadow each other as they mature, diffused lighting tends to fill in some of those shadowed areas that develop as corals grow. Spectrum is very important so regardless of which light source you choose, do your research and provide the spectrums required by the types of corals you are keeping. Strong lighting should be offered when housing SPS coral. A PAR meter such as the Apogee MQ200 should be used to check PAR levels in various areas and levels of the tank.
Skimmer: A good skimmer is necessary for any reef tank however, you should not choose a skimmer that is grossly over-rated for your net water volume or planned livestock. Skimmers that are too large for your system tend to over strip the water, as a result corals will suffer. KZ recommends their Venturi driven skimmers, claiming it is more gentle on plankton and less likely to remove elements from the system. If you choose to use a needle wheel skimmer, as I do, make sure you are skimming dry. Skimming dry will minimize the removal of elements but will also minimize the removal of nutrients. To help solve this issue I recommend cleaning the skimmer neck regularly when skimming dry.
Potassium Test Kit: The specific zeolites used for the ZEOvit® System tend to deplete potassium (K) over time. For this reason it is necessary to monitor potassium levels regularly and maintain 380-400ppm with a potassium supplement like ZEOvit® K-Balance. Some people believe needle wheel skimmers also deplete potassium levels to some degree.
Nutrient absorbers: It is not recommended to use, in conjunction with the ZEOvit® System, any form of nutrient absorbers such as granular ferric oxide (GFO), aluminum based absorbers, or nitrate absorbers of any kind. Use of these products create a competition for nutrients between the ZEOvit® and absorber used. They simple do not work well with the ZEOvit® System and I strongly encourage you not to use them. The ZEOvit® System is more than capable of controlling both PO4 and NO3 on its own, no other products are needed.
Parameters: It is important to maintain natural seawater (NSW) parameters while using the ZEOvit® System, specifically major elements. The reasoning behind this is that anything above NSW parameters will cause stress to corals, especially the sensitive SPS species, in a low or ultra low nutrient environment. Personally I have not noticed any benefits to keeping elevated elements in my systems. I have experienced STN from the base and or tips of SPS corals when elements rose above that of NSW levels. It is critical that you maintain a stable parameter environment, either by dosing manually or by using some type of accurate dosing automation device such as stepper peristaltic pumps, syringe pumps, or other device suited to the type of solution and amount dosed daily.  Stability is vital when keeping corals in a ZEOvit® System.
Salt: In order to maintain NSW parameters it is important to use a salt mix that is balanced in such a way. Most synthetic salt brands boost the major elements contained in their mix, this is problematic for ZEOvit® users because every time a water change is performed an imbalance is created. KZ makes their own salt, which I must say is the best salt I have ever used. KZ Reefers Best Salt (RBS) mixes extremely clean and maintains parameters at NSW levels consistently. Other salt brands can be used as long as they meet the parameter recommendations. Natural seawater can also be used provided it is collected far from shore and comes from a suitable location. Sourcing clean natural seawater is not practical for most people and I have seen no benefits other than cost.
ZEO-Reactor: In order to run the ZEOvit® System you will need a dedicated zeo-reactor, there are many brands and types available - manual and automated versions from Korallen-Zucht or other manufactures in various sizes. If you do not require automation models I recommend the KZ or Vertex brand models. If you require automation, KZ or Avast brands are your best options at the time of this writing. Zeo-reactors in general should provide specific flow rates to the KZ zeolites contained within while allowing for daily agitation (shaking) of the media. (More on this later).
Patience: I cant emphasize enough the need for patients with any reef system, ZEOvit® is no different. It takes time to establish a stable reef ecosystem, often 6 months or more. ZEOvit® is not a plug and playfiltration method, it requires the user to observe and respond based on the look of corals and other organisms in the tank. Daily interaction is often necessary, especially for the first few months. So, it comes to reason this method is not for everyone.
This list is not complete, I recommend downloading and reading fully the Korallen-Zucht ZEOvit® Guide, found on their web site and available in several languages.
Basic Components
ZEOvit® (zeolites): Sometimes referred to as stonesand are the key component to the ZEOvit® System. Korallen-Zucht uses 3 different zeolites found in nature however, approximately 40 different zeolites exist. These 3 specific zeolites perform the simple function of absorption and catalyst. They absorb ammonia (NH4) and provide a surface in which nitrifying bacteria can attach and begin the nitrogen cycle. As the bacteria colonize and multiply on the zeolites they form mulmor bacterial film that can be removed via agitation or shaking (without removing all the bacteria), so they can enter the system suspended and feed corals. This suspended bacteria entering the general system on a daily basis is what sets the ZEOvit® System apart from other bacterially driven systems. It may also be key to the success of the method and health of the corals they feed.
The general rule for the amount of zeolites used is 1L/100USG net water volume. I have experimented with using more than the recommended zeolites, this caused excessive nutrient reduction from the system and the result was necrosis issues on some corals. I think you can safely get away with using slightly more stones (+5%) if your system is heavily stocked with fish but I dont think it is necessary.
The zeolites do expire, usually every 6 weeks, so they need to be replaced accordingly. Much like activated carbon, the pores fill up and the media is no longer effective. 
Flow through the reactor is also vital, the rate at which nutrients are supplied to the colonizing bacteria or if you prefer, how much water travels through the reactor per hour. This rate has to be calculated from actual physical measurement to confirm it is correct. Flow rates have proved to be quite important, too much flow through the reactor will cause nutrients to be overly depleted eventually causing tissue necrosis on corals. Too little flow runs the risk of not removing enough nutrients from the system thus causing nutrients to rise, pest algae to grow, and possible decline of coral (and other livestock) health. The general rule for flow rate through the reactor is no more than 100GPH (~378LPH)/1L of zeolites used. I recommend aiming for less than the maximum flow rate, say 50-90GPH (~190-340LPH)/1L of zeolites used. 
ZEObak: The strains of bacteria present in ZEObak are proprietary as with all the KZ line of products. It is obvious from using it over the years that it is concentrated and very alive. Dosing is done initially, after a new zeolite change, every day for ten days to re-establish the colony on the new zeolites. After the initial 10 days then dosing is performed twice a week, this is just to maintain the strain incase there is die-off. As I mentioned, this is a concentrated product and I do not recommend overdosing this product. Overdose of ZEObak leads to some strange bacterial films on rock or possibly a bacterial bloom.
ZEOstart3: This is really a liquid carbon source or mix of different carbon sources that provide energy to the nitrifying bacteria and insure populations remain strong and consistent. It is dosed in small precise amounts twice daily, again to insure stability of the system through a consistent bacterial population. Recommendations for dosing this product have a maximum dose and minimum dose. The general recommendation is 1mL/100USG net water volume however, it has been my experience this maximum is only needed when the system is new and rock or other components are leaching nutrients. Once leaching has subsided and nutrients are low, using 50% of the dose is usually all that is needed - maybe even less. ZEOstart3 does require some tweaking on the users part as every tank is different, many people have found they need to slowly reduce the amount dosed as the tank ages.
Activkohle: Activkohlemeans activated carbon in the German language and is the name of the KZ brand of carbon. Like all activated carbons it adsorbs toxins, toxic compounds and yellowing compounds and also proteins. This carbon seems to be more gentle, for lack of a better term. KZ recommends against using aggressive carbons that might shock corals, especially when freshly introduced or overused. I have witnessed tissue thinning on SPS with the use of aggressive carbons or even the over-use of gentle ones. KZ recommends using 1L Activkohle/250USG (~946L) of net water volume.
I have found running carbon passively in a mesh bag in a low flow area of the sump to work best for me. Some prefer it in a reactor but I have found corals to react negatively, especially when fresh carbon introduced.
ZEOfood7: KZ describes this product as, “… a multiplication of and food for the dosed microorganisms and a food source for your corals. It enhances the growth of all corals.It really is a mixed bag of products to feed bacteria, corals, and micro-organisms. It has fallen out of popularity lately, mainly because there are so many individual products in the KZ line that feed specific organisms and corals in the tank. It is still a great product and probably the best KZ food product to use if you are not interested in acquiring several additional bottles to feed specifically.
This product is introduced once your system is low nutrient and stable with corals showing bright/pale coloration. It is not used during the 14 Day Cycle.
Sponge Power: This product enhances the growth of sponges and ultimately their water cleaning power. It also enhances SPS growth tips and the colour purple. Overall it is a great product and is used from the beginning of the 14 Day Cycle.
The filtration and cleaning ability of sponges should not be overlooked in any reef aquarium, I have sponges forming in my display that are blue and tubular in shape, the largest one is 5cm tall, really cool, and I have no idea where they came from originally but I believe that Sponge Power is keeping them happy.
These are the basic products/components of the ZEOvit® System, in theory they are all that is needed to maintain a low nutrient system and healthy vibrant corals. Most people do choose to add at least some additional products to their regimen but it is not necessary. I have seen some really nice tanks that only run the basics.
Beyond the Basics
There are a multitude of other KZ products, each with a specific function. Food, trace elements, major elements, problem solvers, and the list goes on. To look at them all for the first time is a bit daunting to say the least. Discussion of these products is beyond the scope of this article but I encourage you to explore further the full ZEOvit® line of products on their web site. In general however, these additional products are added only after the tank has cycled and is running low nutrient stable. In some cases it may be beneficial to dose them before, especially if problems arise.
If you decide to add more products, I recommend adding one product to your regimen at a time, this will allow you to visualize what each product does for your corals. A greater understanding of the overall system will be achieved this way.
Nano Tanks
I am asked quite regularly if the ZEOvit® System can be run on a nano tank. The answer is yesand maybe no. I personally would not run the ZEOvit® on a system that has less than 20USG (~75L) net water volume. I am not saying it cant be done, it would just be very difficult to maintain the stability required for SPS corals.
Due to the requirement of a skimmer and zeo-reactor, nano AIO tanks do not work well, there simply isnt enough room to house the reactor. If you are considering a nano tank with the ZEOvit® System, I recommend having a sump below the display to house all the equipment needed.
One of the biggest issues with any nano reef system is the lack of water within it. The smaller the water volume the more difficult it is to maintain stability within the system. I dont think Thomas Pohl ever intended his system to run on nano systems, it certainly has not been marketed that way. Maybe for good reason, he knows the challenges associated with nano sized water volumes. I know first-hand that it is possible but being able to maintain stability is often challenging, your goal should be to set up a system that can maintain stability. This often means automation, dosing pumps, auto top-offs, and a controller that can manage it all.
For me, the biggest challenge I have encountered when maintaining stability in a zeo-nano tank has been dosing accurate amounts of solution with automation. Most peristaltic pumps are not accurate enough for doses under 1mL, which is often the case using ZEOvit®. Specifically, ZEOstart3 dosing (carbon source) and trace elements where accuracy really matters. To auto-dose very small amounts accurately it is beneficial to use a device like a syringe pump capable of micro doses.
In this article I have discussed the basics of the ZEOvit® System including the recommended requirements for running the system effectively. ZEOvit® is probably not the best option for the first time reefer and may be better suited to someone who already has a good understanding of reefkeeping. It requires, in some cases, a change of old habits as this methodology differs considerably from other methods. A degree of patience is required, as is with all reefkeeping and anything new. I highly recommend downloading the ZEOvit® Guide and visiting the ZEOvit® Forum for more information if you are interested in using this method, they are both invaluable resources of information.

About the author 

Christine "NanoTopia" Lord is a nurse and long time nano reef enthusiast. Recently, her tanks have been featured in the ZEOvit and Nano-Reef aquarium forums. Christine is also a scuba diver (now retired) and has volunteered her time performing underwater educational shows and assisting with research at the Vancouver Public Aquarium.