Wide view of marine aquaria

(photo taken 3-29-99)

Augsburg's marine aquarium system consists of two interconnected tanks, which were custom built to make maximum use of the available lab space. The aquaria are set up in room 225 of the Science Building, which is a teaching lab used for General Biology and Invertebrate Biology labs.

The Biology and Methodology of Reef Aquaria:

Reef aquaria such as our setup at Augsburg are truly state-of-the art aquarium systems. Reef aquarium technology is changing rapidly, and dramatic developments have occurred over the past 10 years (even over the last 5 years!). Amazing reef tanks with incredible biological diversity are now possible. Reef systems like the one we have at Augsburg were virtually unheard of 10 or 20 years ago, and many large public aquaria are only now setting up reef aquaria of this sort. In fact, many of the revolutionary advances in reef aquarium technology were not initially developed in large public aquaria, but rather in the homes of advanced amateur aquarists (certain European aquarists were particularly influential in the early years of reef aquaria).

Several decades ago, the typical saltwater aquarium was a tank for fish, plus maybe a few hardy invertebrates. Standard technology in such tanks used to be an undergravel filter. With these filters, water is drawn through a gravel bed colonized by various species of beneficial bacteria that convert the toxic ammonia produced by fish into less toxic nitrite, and then to the even less toxic nitrate. Some invertebrates can be kept in these old-style tanks, but water quality in such tanks is usually not good enough over the long run (or even the short run) to keep many of the more sensitive invertebrates. Revolutionary improvements in filtration (described below) and other aquarium management techniques have changed things dramatically. For example, it is now commonplace to keep and even propagate stony corals, which were long considered impossible to keep alive in captivity. The result has been that during the last decade or so, there has been an explosion in the keeping of "reef tanks", which essentially create a small, living, thriving bit of a coral reef in an aquarium.

In nature, coral reefs only develop in areas of the ocean with fairly shallow, clean, clear water with good penetration of sunlight. The water must have very low nutrient levels, and the temperature must be warm (but not too warm), and very stable. Given these exacting conditions, remarkable coral reef ecosystems representing some of the most species rich and complex ecosystems on earth have developed in some areas of the tropics. The majority of the world's coral reefs occur in the tropical Indo-Pacific region, with reefs also occurring in the Caribbean, and a few other locations.

To maintain many of the more sensitive reef creatures in captivity, particularly the stony corals that build coral reefs, their very exacting needs must be met. What follows is a listing of some of their major needs, along with brief descriptions of how these needs can be met in a captive environment.

1. Temperature in any aquarium needs to be stable and needs to stay within an acceptable range. Rapid temperature changes (even within the acceptable range) can be deadly. Appropriate temperatures for most tropical marine tanks range from the low 70's (at the lowest), to around 80 - 85 degrees or so, though temperatures in the mid to high 80's may stress some reef organisms and are approaching the upper lethal temperatures for some corals. Many reef aquarists maintain temperatures around 80 degrees F or a little higher. Standard aquarium heaters can deal with rooms that are sometimes too cool, but a chiller is also necessary in a room like Science 225 that sometimes gets too hot.

   At Augsburg we keep our tanks a bit cooler than many reef aquarists, around 75 to 77 degrees F, which helps our fish better handle occassional vacation periods or long weekends without feeding. These lower temperatures also give us a slightly larger margin of safety in the event that our chiller fails during a period of extremely hot weather. (However, one noted author has pointed out that corals routinely kept at and thus acclimated to warmer temperatures are more likely to survive a heat wave, which argues against our lower tank temperatures).

    

2. Salinity needs to stay within an acceptable range and not fluctuate too rapidly. Appropriate specific gravities range from around 1.020 (which is sort of low for invertebrates) to 1.030 or so, with roughly 1.025 considered to be ideal by many reef aquarists. We monitor specific gravity on a regular basis and adjust as necessary.

   The composition of the water needs to be correct otherwise as well, of course. This is typically assured by using a good quality synthetic sea salt mix (we use Instant Ocean), and through regular use of various water supplements as described below.

    

3. pH needs to be correct, and should not fluctuate too rapidly. Natural seawater has a pH of about 8.2, though marine aquaria can range from 8.0 or even a bit lower to as high as 8.5 or so without ill effects. Seawater is naturally buffered, and if a tank is managed properly pH will probably be fine.

   Even so, reef aquarists often utilize a few tricks to help stabilize pH. Though the pH of the ocean is quite stable, pH in an aquarium tends to fluctuate on a diurnal cycle, with the lowest pH of the day just before the lights go on, and the highest pH just before the lights go out in the evening. This is due to changing carbon dioxide concentrations influenced by rates of cellular respiration and photosynthesis in the light vs. the dark. Carbon dioxide in water forms a weak acid (carbonic acid), so the more carbon dioxide in the water, the lower the pH. The animals and algae (and other plants) are all performing cellular respiration and thereby producing carbon dioxide day and night. During the day, however, the algae and other plants are also photosynthesizing (which consumes carbon dioxide), and during the day they are typically consuming carbon dioxide faster than they are producing it. The resulting buildup of carbon dioxide during the night, and its removal by photosynthesis during the day, can cause pH to drop below 8.0 at night, and to rise above 8.5 during the day in aquaria with many photosynthetic organisms. Many reef aquarists dose saturated solutions of calcium hydroxide to reef tanks to maintain calcium and alkalinity levels (see below), and usually choose to do this at night in order to reduce the nighttime drop in pH. In addition, the algae turf scrubber filters discussed below (which use the growth of turf algae to remove nutrients from the water) are normally illuminated at night and kept in the dark during the day. The resulting nighttime photosynthesis by the turf algae counters the nighttime drop in pH by consuming carbon dioxide at a time when no photosynthesis is taking place in the aquarium otherwise (and as an added benefit, the algal photosynthesis also keeps nighttime oxygen levels high).

    

4. Proper lighting is important, especially if a tank includes photosynthetic cnidarians (corals, anemones, etc., many of which are fed by symbiotic algae that live within their tissues), macroalgae (i.e. "seaweeds"), or other photosynthetic organisms. Some organisms need very high light intensities and the proper wavelengths of light. Tanks with photosynthetic cnidarians usually have a combination of white "daylight" bulbs together with "actinic" bulbs, the latter being blue in color. Blue is the color that penetrates most deeply in the water. Accordingly, corals and many other photosynthetic marine organisms photosynthesize most efficiently using these shorter wavelengths of light.

   Lights should be on a normal photoperiod (on a timer), typically 12 hours on and 12 hours off to simulate photoperiods near the equator. Regular photoperiods are important for the normal behavior and good health of the organisms. Furthermore, many reef aquarists turn their actinic lights on an hour or so before the white "daylight" bulbs and keep them on an hour or so after the white lights are switched off to simulate dawn and dusk periods (we do this at Augsburg).

   In recent years, some reef aquarists have begun using computerized controllers to adjust the photoperiods over their aquaria to match the changing daylengths wild corals would experience during the course of the year (some also adjust water temperatures slightly according to season). Some reefkeepers also use a dim incandescent bulb at night adjusted in intensity to match natural lunar cycles. Using these sophisticated lighting controls, some aquarists have succeeded in inducing spawnings of their captive corals (which in the wild are typically seasonal and tied to lunar cycles).

    

5. Control of nutrients in the water is of utmost importance! The high light levels in many reef tanks present an especially great challenge in this regard, since intense lighting together with high levels of nutrients (especially phosphates and nitrogen compounds such as nitrate) fuels the lush growth of filamentous algae, blue green algae, dinoflagellates, etc., all of which can be extremely damaging to the aquarium ecosystem. Dinoflagellates (the free-living types, not the symbiotic zooxanthellae) can be toxic to some of the tank inhabitants, and filamentous algae can cover and smother sessile organisms (sessile = planted in one spot, such as a coral, sponge, tunicate, or macroalgae). In tanks that don't need intense lighting, algae can be controlled to a certain extent simply by reducing the light intensities, but unless you have complete darkness, this is only partially effective. Reef aquarists control nutrients by a variety of means, including the use of protein skimmers or algae turf scrubbers.
   
   
6. Filamentous algae and other problem algae are the enemies of healthy, stable tanks for invertebrates! As discussed above, nutrient control is of utmost importance, and the primary means of algae control. However, the inclusion of certain herbivores is critical as well. Most reef aquaria have herbivorous fish such as tangs or blennies, as well as significant numbers of herbivorous snails for algae control.
   
   
7. Trace elements typically get depleted by uptake by organisms and by other processes. Though the matter of trace element additions is currently in hot debate among reef aquarists, noted authors have made strong arguments that it is prudent to maintain trace elements at or near natural levels. Trace elements can be maintained in several ways. Some aquarists simply do regular partial water changes using fresh seawater (normally synthetic seawater is used), which helps to maintain proper ionic balance in the aquarium. Some authors have argued that regular feeding of an aquarium replenishes most trace elements adequately. However, many aquarists also make regular additions of trace element supplements. Iodine is generally considered to be important for some marine invertebrates and for certain red macroalgae. Iron is generally considered to be important for some corals (e.g. Tubipora sp.) and many of the marine plants such as turtle grass, macroalgae, and turf algae.

   In reef tanks, which typically have high densities of calcifying organisms (e.g., coralline algae and stony corals, both of which create calcium carbonate (limestone) skeletons as they grow), proper levels of strontium are also very important. In fact, stony corals in the genus Acropora were considered to be impossible to keep in aquaria until their need for strontium was recognized. Many reef aquarists add strontium on a regular basis, using either a strontium chloride solution or a commercial trace element mix that includes strontium along with iodine and iron and a variety of other trace elements. Other aquarists depend upon release of strontium from their sandbeds as the sand gradually dissolves, or regular water changes as described above (the dosing of strontium is also in hot debate!)

   Also, calcium and carbonate ions are consumed rapidly by calcifying organisms and need to be replaced. Carbonate ion levels are linked to the alkalinity of the water (alkalinity roughly equals the buffering capacity of the water...the ability to absorb and neutralize acidity). Higher alkalinity values generally are associated with greater carbonate ion availability, and high alkalinity values tend to stabilize the pH, keeping it near normal seawater levels.

   One standard and very good method for maintaining calcium and alkalinity levels is to slowly drip in a saturated solution of calcium hydroxide (referred to as "kalkwasser" by the German reef aquarists who devised this method), replacing all of the water lost to evaporation with the calcium hydroxide solution. Incidentally, if the calcium hydroxide is added too quickly, the pH rises too high, which causes calcium carbonate to precipitate out of the water (looking like a snowstorm in the tank), and reducing rather than raising calcium and alkalinity values! This is why it needs to be dripped in.

   Other methods of maintaining calcium and alkalinity levels have now been developed, some of which can be easier to implement. However, even when using these other methods, many reef aquarists still like to use calcium hydroxide, since calcium hydroxide has the added benefit of tending to precipitate phosphates, making the phosphates unavailable to algae.

    

8. Control of the toxic nitrogenous wastes from animals and decomposers is extremely important in any aquarium. Proteins and nucleic acids (both of which are present in all organisms) are digested and broken down by animals or decomposers (e.g. bacteria, protists, and fungi). The initial step is the removal of the nitrogen from these molecules. This nitrogen is released in the form of ammonia, which is very toxic, and ammonia can build up to toxic levels in an aquarium system. To deal with this problem, the ammonia needs to either be consumed by plants, or it needs to be converted first to nitrite (which is less toxic than ammonia) and then to nitrate (even less toxic) by specialized bacteria called nitrifying bacteria. Aquaria of all sorts are dependent upon healthy populations of these nitrifying bacteria, which are cultivated in various biological filtration devices. These bacteria require oxygen for growth, and they typically live attached to surfaces (as do most bacteria in nature), so biological nitrifying filters generally consist of some sort of high surface area substrate for bacteria to colonize that has oxygenated water flowing over it. Undergravel filters, which revolutionized aquaria in the 1970's, suck tank water through a gravel bed, thus fostering the growth of nitrifying bacteria on the surfaces of the gravel particles. Wet-dry filters trickle tank water over a non-submerged gravel bed or some other looser substrate with a high surface area, thereby providing really good oxygenation for the bacteria and thus greater filter efficiency. The "Bio- wheel" filter on the market these days is a very efficient variant of this general approach.

   Really good, active populations of nitrifying bacteria prevent captive aquarium animals from dying from ammonia poisoning, but they do produce a lot of nitrate. Removal of this nitrate is one reason for doing regular partial water changes in the typical freshwater aquarium. In a brightly lit aquarium such as a reef tank, however, this nitrate (if allowed to build up) helps to fuel the lush growth of various algae that are often harmful to the aquarium system. Thus, reef tanks need to employ various methods for reducing nitrate production in the first place, and for removing the nitrate that is produced.

   One way to reduce nitrate production is to reduce ammonia production by limiting food inputs into the system. (this also reduces the buildup of phosphates and other nutrients, which are also released from food as it is digested and/or decomposed). For this reason, most reef systems have very low populations of fish and other animals that need to be fed, and have photosynthetic organisms such as corals as the predominant life forms.

   Another way to manage nutrients such as nitrates (and other nutrients) is by increasing nutrient export from the system. The bottom line is that exports must at least match imports, otherwise nutrients will build up in the system and fuel rampant algae growth. In the case of nitrates, the incorporation of an anaerobic sand bed will foster the development of populations of denitrifyng bacteria, which convert nitrate into relatively inert nitrogen gas. This nitrogen gas cannot be used by plants as a nutrient, and it is dissipated from the system into the air. This denitrification function of anaerobic sand beds is one of the main reasons we have thick layers of fine sand in both of our aquaria.

   Most (all?) successful reef systems these days have most of their nitrifying activity and some of the denitrifying activity provided by what is commonly referred to as "live rock". Live rock is porous calcareous rock (typically dead coral rubble collected near reefs) that is heavily colonized by diverse organisms, most importantly coralline algae (which tend to inhibit the growth of harmful filamentous algae), and an abundance of bacteria. Nitrifying bacteria live on the external surfaces and oxygenated recesses, with denitrifying bacteria present in the adjacent, inner anaerobic regions. Thus, the thinking is that live rock provides "one-stop" conversion of ammonia, to nitrite, to nitrate, to nitrogen gas, thus effectively keeping much of this nitrogen out of reach of harmful algae. Beneficial coralline algae also are taking up ammonia directly, which helps as well.

   Another technique commonly employed to maintain excellent water quality is the use of protein skimmers. Protein skimmers are devices that mix enormous amounts of tiny air bubbles together with tank water in a special mixing chamber. Dissolved organic compounds such as proteins, nucleic acids, carbohydrates, etc. precipitate out as a film on the bubble surfaces, forming a thick foam which spills out of the top of the protein skimmer. These organic compounds are largely the products of food digestion/decomposition. Protein skimmers remove them from the system before they have the chance to be broken down completely by bacteria. This is important, since complete breakdown would release simpler nitrogen compounds, phosphates, and other nutrients into the water, making these nutrients available to algae.

   The use of activated carbon also accomplishes similar goals, and is often used hand in hand with protein skimmers. Activated carbon can also remove certain compounds that are not removed by protein skimmers.

   More recently, reef aquaria have been set up using algae-based filters of various sorts. In algae turf scrubbers, for example, the growth of certain types of algae called turf algae is encouraged on a plastic screen. Turf algae are extremely efficient at taking up nutrients from the water, and their growth reduces nutrient levels to very low levels that starve out most of the potentially harmful algae that can plague badly managed reef tanks. Periodically (ideally weekly), the turf algae are scraped off the plastic screen and removed from the system. This very efficiently exports large amounts of nutrients from the system and keeps nutrient levels in the water extremely low. The nutrient uptake ability of a good algae turf scrubber is prodigious, which allows tanks with algae turf scrubbers to be much more heavily stocked with fish and more heavily fed than the more traditional reef tanks employing just protein skimmers.

   Tanks with algae turf scrubbers typically use large amounts of live rock (approx. 1 pound per gallon) just like any other reef system, but they are usually run without protein skimmers (a sacrilege in many people's minds!), which is how our tanks at Augsburg are currently being managed. The advantage of not using a protein skimmer if you don't need to is that this avoids some of the negative aspects of protein skimmer use. The potential harm done by protein skimmers includes the removal of fine particulates (including bacteria) that could otherwise serve as food for filter-feeding animals, the removal of trace elements (algae scrubbers remove trace elements as well of course), and the removal of larval stages of various organisms.

    

9. An additional critical requirement for a healthy reef aquarium is good water movement. This is particularly important for many sessile invertebrates such as sponges and corals, many of which will die without good water flow. Ideally, water currents should be intermittent and changing, simulating natural surge and flow patterns that would be experienced at a reef. Different species require different flow patterns, some requiring strong surges, others tolerating or even prefering gentler conditions. Precise placement of corals, anemones, sponges, and other sessile invertebrates in the aquarium is absolutely critical; seemingly subtle differences in water flow (and lighting) between different microenvironments as little as a few inches apart can make all the difference in determining the success or failure of a sessile invertebrate.
   
   
10. Oxygen levels must stay high. Good water flow helps in this regard. Protein skimmers and/or algae turf scrubbers also are very effective at oxygenating the water.

Technical Details of Augsburg's Marine Aquarium System (also see Aquarium wide view photo):

Reef Aquarium Specifications:

• Dimensions of tank: 30" x 28" x 23" (length across front x front to back dimension x height)
• Lighting: One 400 W 6500K metal halide bulb, plus two 96 W VHO fluorescent blue (actinic) bulbs.

Seagrass Aquarium Specifications:

• Dimensions: 24" x 28" x 23" (l x w x h) (length across front x front to back dimension x height)
• Lighting: One 400W 5500K metal halide bulb, plus two 28 W power-compact actinic bulbs.

Sump:

• A 20 gallon sump (normally about 1/2 full) on the floor receives all return flow from both aquaria, and houses all water pumps, a heater, water flow to and from a chiller, and inlets from several dosing pumps.

Total system volume:

• Approximately 130 gallons
• Volume is less than tank dimensions would suggest because water level is approximately 4 inches below the tank tops to reduce the likelihood of fish losses due to jumping and to reduce escape of salt spray from the open-top tanks.

Water circulation:

4 Mag Drive 7 pumps located in the sump provide water circulation.

• One supplies water to the algal turf scrubber (Inland Aquatics Model 250), which dumps directly into the back right corner of the reef tank, creating strong water surges.
• Two other pumps return water directly to the tanks. Part of the flow of each pump goes through either of two Sea Swirl oscillating units, each of which rotates the water return back and forth over 100 degrees. One oscillating unit is in the front left corner of the reef tank, while the other is in the front right corner of the seagrass tank (the seagrass tank oscillating unit was not installed when this photo was taken). The remainder of the flow from the two pumps comes in through bulkheads in the top, back center of each tank. In the reef tank, this water flow is directed straight down behind the rockwork. In the seagrass tank, 1/2" "flexipipe" (with several Y connectors, valves, and multiple outlets) is used to carefully direct and manipulate water flow in the vicinity of certain large sponges.
• The fourth pump supplies water to the chiller (this water returns directly to the sump).

The two tanks are also interconnected by two 1" water lines that go between bulkheads in an overflow box on the left wall of the reef tank and bulkheads on the right wall of the seagrass tank. Water flow directly between the two tanks occurs because the overflow boxes in the seagrass tank are mounted lower than the water level of the reef tank. One of these overflows is 1/2" lower, while the other is 2" lower (only one overflow is used at a time, and choice of overflow box determines rate of direct flow between tanks). Originally, the seagrass tank was set up as a refugium of sorts for larval stages from the reef tank. It contained no fish, had gentle water flow to accommodate delicate Cassiopea jellyfish, and all water flow through the seagrass tank came directly from the reef tank. This arrangement was discontinued after about 7 months, but the water lines directly between the tanks still provide a valuable margin of safety against stagnant water conditions in the seagrass tank should its water return pump fail over a long weekend.

Filtration: All filtration is provided by an Algal Turf Scrubber (Model 250), manufactured by Inland Aquatics in Terre Haute, Indiana (www.inlandaquatics.com). This algae filter is based on designs developed by Walter Adey at the Smithsonian Institution. The algae turf scrubber is the large black box visible in the Aquarium wide view photo above the reef tank (and behind the reef tank's light).

• Algal Turf Scrubbers utilize highly efficient turf algae to remove nutrients from the water. These algae are grown on a plastic screen in a long, shallow rectangular tray (dump bucket) resting on a pivot rod that allows the tray to tilt. Water is continuously pumped into the tray. When the tray is full (about every 40 seconds in our case) the center of gravity shifts, causing the tray to tilt, and approximately 1 gallon of water is dumped into the aquarium. The water surges within the tray greatly increase growth rates of the turf algae, thereby improving their efficiency at removing nutrients from the water. As a secondary benefit, the dumping action provides extremely beneficial water surges within the reef tank that simulate the natural water motion experienced by corals on a coral reef. (see the "Water surging into reef tank" photo).

• Our algal turf scrubber has been in operation as the sole filtration on the tank since August 1998.
  
  Within the first 9 months only about 10 gallons of water were changed. During the summer of 2000, three water changes (approx 20% each time) were made as a precautionary measure to help to correct any ionic imbalances that might have developed in the system over time. More frequent partial water changes would probably be beneficial to guard against ionic imbalances developing (we simply haven't gotten around to doing them), but there has been no indication that the system has needed more frequent water changes.
  
  
• Prior to installing the algal turf scrubber (i.e., for about 1 year), we used a downdraft protein skimmer (model: ETS 700). During much of this time period, the system was plagued by serious algae problems, including lush growths in both tanks of Cladophora, a prolonged dinoflagellate bloom, and less serious but still troubling blooms of Ceramium in the seagrass tank (the tangs eagerly consumed all Ceramium growth in the reef tank, but would not touch the Cladophora). Within one week of the proper algae becoming established in the algal turf scrubber, the troublesome Cladophora growths in both tanks started to die and slough off the rocks. Within 1 to 1.5 months, almost all was gone. Aside from occasional, non-problematic, temporary growths of a brown or red cyanobacteria on the sand in some areas after periods of excessive feeding, there have been no new outbreaks of problem algae, despite a substantial fish population. Our fish are normally fed every weekday (most weeks on weekends as well), usually several times a day, and they are well fed.

• Note: The superior control of macronutrients (e.g. nitrates and phosphates) by the algal turf scrubber allowed us to use much higher doses of trace elements, which we strongly suspect is responsible for dramatically improved growth of turtle grass and certain red macroalgae. Prior to the algal turf scrubber, it was our impression that high doses of trace element supplements such as Combisan contributed to problem algae growth, so these supplements were used very sparingly. During this time, the turtle grass and Wrightiella barely grew, and the turtle grass seemed to be in a state of decline. Several months after the algal turf scrubber was well established, we began using several trace element supplements (mostly Biotrace , sometimes alternating with Combisan) at their maximum recommended dosages. This was associated by a rapid increase in growth rate of turtle grass and certain red macroalgae. The turtle grass has been growing vigorously ever since. It is over 2 feet tall, and is sending up new shoots from rhizomes that are expanding under the sand.
  
  
• Note that there is NO mechanical filtration in our system to remove particulates from the water, though sediments that settle in the sump are siphoned out every 6 months or so.

Replacement of Evaporated Water, Calcium and Alkalinity Management, and Trace Element Additions:

A 44 liter rectangular plastic storage container is used as a reservoir for water to make up for evaporation. To deionized water we add calcium hydroxide (in an amount in slight excess of what will go into solution). Previously, we also added strontium chloride and potassium iodide to the reservoir, but this was discontinued after we began regular use of Biotrace and Combisan (see below). A floating styrofoam lid minimizes contact with air, which reduces the usual formation of calcium carbonate on the surface that normally occurs as carbon dioxide is absorbed by calcium hydroxide solutions. The calcium hydroxide solution is pumped slowly into the sump by a "Reef filler" dosing pump (from Champion Lighting). This pump is controlled by a SpectraPure water level switch mounted in the sump, which is plugged into an X-10 control module. This control module is controlled by a Neptune AquaController, which monitors aquarium pH and turns off the dosing pump if the pH exceeds 8.5. The reservoir normally needs to be refilled 2 or 3 times each week.

Additional calcium and alkalinity management is accomplished by adding 40 ml each of part A and part B of C-Balance each morning. This is accomplished using a two-head ReefFiller pump on a timer. It is possible that our total calcium additions are excessive relative to the needs of the system (we have not adequately explored this issue), and perhaps either the calcium hydroxide OR the C-Balance would be adequate. However, our general impression has been that the C-Balance additions improve the growth of coralline algae in our system.

Calcium and alkalinity values are normally about 425 mg/l and 172 ppm (3.44 meq/l), as measured by Salifert and LaMotte test kits respectively. pH is normally 8.2 to 8.3 at night, and approximately 8.5 late in the day.

A trace element mix (usually Biotrace, occasionally Combisan) was used at the maximum dose recommended by the manufacturer (with the weekly dose split between Monday and Friday additions) until the beginning of Summer 2000. All trace element additions were then stopped for several months because we suspected iodine levels might have gotten too high. We did not have a reliable test kit to check this, but various shrimp in the tanks seemed to be having molting difficulties (e.g. crooked antennae), and such molting problems have been reported as being associated with iodine levels that are too high (alternatively, we had had the shrimp for several years, so possibly the shrimp were simply getting old???). In October 2000 we resumed use of Biotrace, but at half the previous dosage.

Temperature Control:

Temperature is kept between 75 and 77 degrees F by a heater and a chiller.

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