Live Sand Filtration A. Thiel In previous installments of Live Sand filtration systems we have analyzed the various methods used, here in the USA, to set up live sand systems and aquariums using a combination of live sand and live rock. or hybrid systems as we called them. We also looked at the sand bar concept, a type of set up where only part of the tank is used as a live sand area, whereas the rest of the aquarium is filled with live rock. Typically this sand bar is in the front of the tank and divided from the rock with an acrylic separator. There are a few variations we have, however, not looked at: - aquariums where the live sand is the predominent form of filtration (with or without plenum but with foam fractionation) - aquariums where rock is used but not to the degree that it is in hybrid systems (again with or without plenum but with protein skimming) - aquariums where even foam fractionation is left out after the initial phase of cycling and maturation have taken place - aquariums where foam fractionation is not used at all and where the only form of current is provided by the use of the injection of air - aquariums using a combination of the above methods where carbon dioxide is injection as well. It is, in my opinion, not necessary to cover each of these type of aquariums separately. What we can do, however, is look at the merits of the changes introduced by themselves, and discuss their impact on the filtration and water quality. When more emphasis is placed on the live sand as the main filtration medium, it becomes that much more important, of course, to ensure that the sand used is truly "live", meaning that it is populated with many animalcules that keep the sand in constant motion and aerate it, so to speak, thus ensuring that no anaerobic activity sets in and that sufficient amounts of oxygen are always present in the sand to ensure nitrification and denitrification, the latter occuring in an anoxic or hypoxic rather than an anaerobic environment. More often than not, hobbyists practising this method will supplement their live sand with additional animals. This includes but is not limited to, brittle and very small red and black sea stars, burrowing snails, many forms of worms and so on, to ensure that these additions move and stir the sand and bring a new and constant small amount of oxygen even in the deeper layers. The addtional population of burrowers and stirrers is normally added once the biological cycle is completed. Note though that with true live sand, this biological cycle is usually barely noticeable. The levels of ammonia and nitrite detected in these systems is very very low. The cycle progresses very rapidly and usually only lasts from a few days to a week. This is, of course, due to the many nitrifying bacteria already present in the sand. Whenever one skews the filtration more towards the live sand part of the system, one needs to ensure that the live sand is really live. One also needs to add additional animals at a later stage, as explained. In some systems live rock is used but not to the degree that it is in so-called Berlin Method type systems. Instead of adding 1.5 to 2 pounds of rock per gallon that the tank is rated at, hobbyists may only use half a pound or less and do so mainly to give the aquarium a reef look and have areas where to place their corals. In such tanks the filtration again relies heavily on the biological action of the sand and the comments made above apply. Add plenty of burrowers and sand stirrers, and do so after the biological cycle has run its course, whether this takes a few days or a week or more (in most cases it will happen rather quickly as we have seen earlier). Should you use a plenum (void space underneath the sand) or should you not? That is still a matter of much debate here in the USA and not everyone is convinced that the plenum is really necessary. Many have set up tanks with sand layers simply placed on the bottom of the tank and report excellent results with these systems as well. The important observation that needs to be made when such systems are used, is that the sand layer thickness should be built up gradually and should not be so thick that its lower levels become devoid of oxygen and lead to the production of hydrogen sulfide and possibly methane, due to anaerobic activity. If this happens you are likely to experience a wipe-out or total loss of all animals. Start such systems with small amounts of live sand and keep adding to it as time goes by, until you have a total thickness of about 2 to 2.5 inches. Recommendations here are often to start with a real thin layer, e.g. half an inch, and build the thickness of the live sand layer up by quarter inch increments at at time, every few weeks or so, making sure that no areas discolor as this would be a sign that a lack of oxygen exists. Add plenty of diggers and burrowers as soon as ammonia and nitrite show zero ppm results when testing for them. Test frequently, especially in the beginning, to allow you to intervene immediately should anything run out of hand. Stir the sand yourself with a think piece of wood or stainless stell to introduce oxygen in the lower areas and so until you have added animals that do so. When sand is placed directly on the bottom of the tank, and no plenum is used, real thick layers of live sand can, in my experience not be used. This, then, limits the bioload that the tank can hold. Indeed, with less nitrification and denitrification area the population in the tank has to be kept a lower levels. To summarize, I much prefer to install a plenum and be able to load up the aquarium with plenty of animals because the biological activity of the sand (and the rock) can cope with such hihger amounts of fish and invertebrates, crustaceans and the like. Let’s face it, we all start with low populations but eventually end up with high ones. Each trip to a pet store seems to result in one more animal added to the tank because we could not resist buying it. Thus, systems that started off with a low biological load end up being taxed each time new animlas are added. The hobbyist must ensure that the filtration used is adequate and commensurate with these higher population loads. In all cases pH control is a major factor. Complete buffers need to be used (personal communication with Andy Hipkiss) from time to time to ensure that no large swings in pH occur. Such buffers are best dripped into the system after diluting them in treated water rather than adding them all at once. The idea behind these additions is to promote the formation of HCO3 ions (bicarbonate ions) which help stabilize the pH. Borate should be a part of such buffers as well and can be used in various forms. I prefer to drip in boric acid myself (diluted first in lukewarm water). The addition of Kalkwasser by the drip method will ensure that the pH remains high. Let’s face it though this is an artificial means of maintaining a high pH and not a natural one. Just stop the limewater addition for a few hours and watch your pH drop. This in itself demands that we resort to additional methods to maintain an adequate pH by buffering the water properly. This can only be achieved by using complete buffers (there are plenty for sale, make sure the label states that they contain borate as well or drip diluted boric acid into the system to achieve the same results). So should you use a plenum or not? My recommendation is to use one as such systems have proven to be safe over the long run whereas systems without plenums are still in their beginning stages and many factors that influence how their water chemistry behaves still have to be discovered so to speak. Two new trends have evolved overseas: not using a skimmer at all after the initial biological cycle has taken place and injecting carbon dioxide into the system. Not using a skimmer cuts out one more external device and put the burden of filtration totally on the live sand and on the live rock (whatever amount is present). My personal experience with such systems has not been very positive. I have found that yellowing matter will soon accumulate and that carbon needs to be used (one to two ounces per 100 liters of water). Additionally it appears that more frequent water changes are necessary in such systems because toxins and noxious elements tend to build up rather quickly (usually in a matter of weeks). Whereas is systems where foam fractionation is used a 5 percent water change every two weeks or so, seems more than adequate, aquariums that are not equipped with skimmers seem to require much more frequent water changes and much larger ones at that too. To maintain a healthy environmnet in such test aquariums that I ran, I had to resort in most of them to performing 10 percent water changes weekly, lest the water take on a real yellowish/brownish color nothwithstanding the use of activated carbon that does no leach phosphates in the water. Hand in hand with this build up of yellowing matter (Gilvin) the corals seemsed to be affected and did not open up as much as they do in systems where strong foam fractionation is use. In this respect TAT has introduced a brand new venturi skimmer, designed to deal with the special requirements of Live Sand Filters. This skimmer is available in the U.K. through Global Aquatics. The addition of boric acid is a new concept that, to my knowledge, originated with yours truly. It has given me excellent results in terms of pH stability and minimizing day/night pH fluctuations, eliminating yet one more stress factor from the aquarium. The dilution rate I use is 1 heaping tablespoon per gallon of water (3.785 liters). The drip rate needs to be adjusted to the size of the system and this will be a bit of a trial and error exercise for you in the beginning. In my 500 galllon show tank I drip 45 drops per minute continuously, although I have experimented with turning the drip off at nite since, at night, carbon dioxide is produced in the system on a continuous basis during night time thus increasing the bicarbonate addition to the water in the tank naturally. You may wish to experiment with both methods and determine which one seems to give you the best results. Ideally I am looking for a morning pH of around 8.2 and an evening one, before the lights go out, of 8.4 or thereabouts. I have let the pH rise to 8.5 without any ill effects. Since we are talking water quality parameters it is probably a good idea to give you some other readings obtained in live sand filters: pH was mentioned above, temperature around 82 degrees maximum, dkH of around 6 to 6, calcium ion content between 450 and 500 ppm, specific gravity of 1.024 to 1.025, redox potential attained naturally without the use of ozone, around 360 in the AM and around 340 in the PM. Minor variations from tank to tank will occur depending on the amount of live sand in the tank. I have one 20 gallon test tank where the ORP is always over 400 mv. Skimmers are in my opinion still an integral part of the reef tank and until more evidence surfaces that we can actually safely do away with them, my recommendation is to maximize protein skimming by using a real powerful foam fractionator. There is now such a wide choice availabe to you that you should not have any problem matching up your system with the right skimmer. Keep in mind though that more powerful skimming requires that you keep a close eye on the additives you use. Indeed skimmers remove many noxious compounds but remove beneficial ones too. Set up a regimen of what you will be adding and adhere to it through thick and thin. Necessary additives include Kalkwasser, Iodine, a complete general purpose additive and eventually boric acid or borate as well as a complete seawater buffer. Note that although I may not have mentioned this up to now, modern aquariums do not include mechanical filtration. We wish to leave a much live animalcules in the system as possible for filter feeders. We also rely on detrivores to take care of whatever particulate matter needs to be removed from the system. Detrivores include small crabs, blue legged hermit of the _Clibinarius tricolor_ variety, and if you need to control coralline algae growth because it is getting out of hand a few _Calcinus tibicen_ hermit crabs. I aslo add many _Holothurians to my system. Most bury during the day but come out at night. For algae control one can use _Astrea_ snails rather than Turbo grazers. I find that the former live longer and are much more active. Snails seem to disappear among the rocks or decide to congregate on the tank’ panes. When they die, often in totally inacessilbe places they add a great deal pollution to the tank. More pollution is the last thing we need! Most of the animals mentioned are available in the UK. You can eMail me at the addresses at the end of this article for more information or with questions if you wish. I will be pleased to try and help you out if I can. Last, but not least, the addition of carbon dioxide. This trend was apparantly started in Germany and was related to me in a personal communication with Alf Jacob Nilsen. Although the addition of CO2 during the day time will have two effects: stabilizing the pH and adding bicarbonate ions to the water, the implementation of such a system requires pH controllers, CO2 equipment, check valves and so on an adds quite a bit of expense to the cost of setting up the tank. Since I have found that I can achieve the same results by adding Boric acid I see no reason at this point in time to resort to CO2 injection, although it certainly is a method that can be used. This concludes the series of articles on Live Sand fitration. I hope they were informative and give you a better idea of what is done on this side of the Ocean. I would be most pleased to answer any questions you have. Here is how to contact me: - through the magazine - on Compuserve I.D. > 76397,2000 - on Internet > tat@3pco.net or athiel@ix.netcom.com Good reef keeping and till next month. Albert J. Thiel