Bsen 5510 crayfish REPORT

7 DAY CLOSURE

December 3, 2014 TEAM CRAWDAD – victoria BURNETT, alexus BROWN, andrew YOUNG, michael CLARK Auburn University

ABSTRACT

Ecological engineers focus on interactions within and between biological and ecological systems. They must apply ecological principles in some goal or service within a system. The semester project is creating an enclosed ecological microcosm revolving around the health of a crayfish. This project uses principles of ecological engineering to create an enclosed water tank that will support all the necessities for the life of a crayfish for a week. The tank will include several abiotic and biotic components and will be monitored for dissolved oxygen, pH, nitrate, nitrite, alkalinity, temperature, ammonia and phosphate to ensure the crayfish proper health.

INTRODUCTION

Crayfish resemble small lobsters and are also known as crawfish, crawdads or mudbugs. They breathe through gills and are found in fresh water bodies. They are often found in the wild, used as bait, and often eaten at crawfish boils. They also can be kept as pets in freshwater aquariums, which is the objective of this project. Normally, these aquariums are open to the air and allow for regular feeding. The purpose of this project is to use a creative ecological engineering background to enclose a 10 gallon tank in a way that will support the life processes of one crayfish for 7 days. The tank will be a closed system, meaning that no material fluxes or matter will pass the boundary of the tank dimensions. However, energy will be able to travel across the system boundaries. Several aspects are taken into account when creating this ecosystem, such as the layout of the tank, biota and abiotic factors, and monitoring of the crayfish itself to ensure its well-being. These aspects are discussed further below.

ALEXUS STUFF-----

The increase of aquatic plants into the microcosm provided more dissolved oxygen into the system. We experienced a steady decrease in the oxygen levels from the one day closure so; it was decided to add more plants to try to keep the oxygen balanced during the 7 day closure. The addition of alligator weed proved to be what was needed to keep the concentration of oxygen at a safe level. Although the concentration decreased it began higher that our first two closures leaving room for declination. There also was a day/night cycle established using a timer to control the lamp. The crayfish seemed to emerge more during the night cycle, which is consistent with research done that’s shows they crayfish are more active at night to reduce the chance of predation. Our crayfish also molted for a second time during the 7 day closure, there is no numerical evidence to support why this occurred but we can assume that it was just increasing the size.

In reference to the biotic and abiotic components introduced into the microcosm, the duckweed that was originally put into the tank decreased tremendously after the first closure. This could be related to the issue of extreme algae growth we encountered after the first closure. We had to clean out the tank and because of that we lost a great bit of the duckweed and the rest dried out because of the decrease in water level after sampling. To compensate for the loss extra alligator weed was put in. The crayfish feed mostly on the plants and it may have caught a water beetle, but most of the water beetles remained in the tank. The snails didn’t seem to do much initially but it may have played a major role in keep down the algae growth on the glass of the tank why the usually moved around, and the production of ammonia which varied throughout the closure. The presence of shrimp was not included into the 7 day closure, not because of issues created by them but simply because they were sold out everywhere before we closed, the ones that were previously included where either eaten by the crayfish or died during the cleaning of the tank.

The overall results of the 7 day closure were proven to be efficient to keep the crayfish alive and also ensure the life of the components included in the system. In retrospect I wouldn’t have included the duckweed initially it was proven to be much more trouble than good. Also the inclusion of the shrimp didn’t change any of the water quality parameters, so they could have been excluded from the microcosm. In all I think we tried for include more things that were technically necessary in the beginning but after testing we were able to narrow down just the important components.

ALEXUS END

MAJOR CRAYFISH HEALTH COMPONENTS

Crayfish are a part of the phylum Arthropoda, meaning jointed foot animals. Their bodies can be divided into segments, with the exception of the abdomen. Their exoskeletons are made of chitin, which is a complex chemical compound incrusted with calcium salts which contributes to the hardness of the shell. Calcium available to the crayfish is important because of this. Oxygen regulation is also important for a crayfish’s health to thrive. The circulatory system distributes oxygenated blood to different organs of the body, and the deoxidized blood returns to the gills where it receives oxygen and the circulatory cycle begins again (Pohl, 1987).

Fresh-water crayfish live in various environments. The typical habitats of the crayfish are lakes, creeks, rivers, natural pools, and small ponds situated in the forest and fields, also they tend to live in man-made reservoirs. The greatest importance that contributes to the crayfish habitat are factors of inorganic nature such as, content of oxygen, water temperature, degree of pollution an type of subsoil. The animate inhabitants, such as fish, flora, and zoo-plankton, of the water body also help determine the conditions of life for the crayfish (Pohl,1987).

Crayfish are more susceptible to oxygen deficiency in water than fish. A content of oxygen of 8.0-10.0 mg/L is reported to be optimal. When it begins to decrease below 2.0 they soon cease to live. Waters with permanently cold temperatures are unfit. Temperatures between 18˚ to 20˚ C are most favorable. Waters also much contain medium contents of calcium compounds, their exoskeletons are made of chitin, which is a complex chemical compound incrusted with calcium salts which contributes to the hardness of the shell (Pohl, 1987). This contributes to the hardness of the shell. Water hardness is important in the molting process of the crayfish.

The subsoil of the microcosm plays an important role for crayfish that spend time in burrows. The most suitable is a compact bottom composed of loamy sands. For our microcosm, we used Zoo MED Hermit Crab Sand and soil from the fisheries pond. The soil from the fisheries pond provides nutrients and flora from a natural crayfish ecosystem. The aquatic plants are also a necessary element in a microcosm; the Duckweed and Ludwigia, not only add oxygen to the closed environment but serves as a major component in the crayfish diet. Crayfish have been defined as polytrophic meaning they are herbivores, predators, and detritivores. To account for all these feeding habits we added Ghost Shrimp, Gold Inca Snail, and Zebra Snail. Although adding these elements will increase the oxygen demand, they provide the crayfish with a reliable food source.

SKETCHES

MATERIALS LIST

Spring Water and Pond Water

Rocks

Sand - Zoo MED Hermit Crab Sand and Aquarium Sand

50 Watt Sun Lamp

Top Fin Mini Aquarium Air Pump

Gold Inca Snail (2)

Ghost Shrimp (6)

Living Plants – Duckweed and Ludwigia

PRELIMINARY BIOTA LIST

1. Abiotic Factors

Water

A volume of water was taken from the water-body in which the crayfish originally lived. This is the pond located at the fisheries department on South College in Auburn, Alabama. Bottled spring water was mixed with the pond water. The ratio of pond water to spring water was 1 to 5. The total amount of water in the tank is

Rocks

There is a mix of large and small rocks that were taken from the Parkerson Mill Creek. The rocks provide shelter for the crayfish to hide under and between. The rocks do have some algae and nutrients on them, providing the ecosystem with small bacteria that would be native to their original environment. This helps increase the nutrient loading of the tank.

Sand and Mud

Crayfish enjoy burrowing underground, especially when water gets cold. This is their natural source of protection from their environment. There are two sources of sand within the tank. The hermit crab sand is used for burrowing, but is mixed with natural aquarium sand so that the crayfish is able to handle and lift larger pieces of sand that are coagulated together. Approximately 0.20 gallons of mud from the fisheries pond on South College in Auburn is also added. This 1.52 kilograms of mud is added to increase the nutrients and compatibility of the sand (Hand, 2013).

Light

Determining the photoperiod is a vital component of the system. The broad spectrum light provides the energy that the plants need to perform photosynthesis. Since oxygen is a limiting factor in a closed ecosystem, the oxygen production should be as great as possible. Allowing daylight for 24 hours in the system will ensure maximum oxygen production. However, the health of the crayfish will suffer if there isn’t a dark period (Stephens, The specimens that were kept in continuous darkness were found to have the lowest molting and mortality rate, 0% and 13%, respectively. Specimens that were exposed to 20 hours of light and 4 hours of darkness had molting and mortality rates of 40.6% and 28%, respectively. Specimens exposed to constant light had molting and mortality rates of 54.4% and 62%, respectively. A light cycle of 20 hours of light and 4 hours of darkness was selected for this system due to the relatively low mortality rate associated with the photoperiod. The 4 hours of darkness was enough time to allow the crayfish to conduct its nocturnal behavior. The stress relief provided by the darkness is essential to the health of the crayfish. This photoperiod allows a maximum amount of light to ensure sufficient oxygen production in the closed system.

Plants will respire at night just as every other biotic component in the tank. This is our reason for keeping our light currently on the plant side of the tank approximately 18 hours a day. This should keep the plants from respiring as much and keep the oxygen production active (Seyffarth, 2012). The light was turned off for 6 hours every day in order to keep the crayfish stress levels down and to prevent premature molting.

Top Fin Mini Aquarium Air Pump

An air pump helps to increase the dissolved oxygen to the entire tank and also provides high amounts of oxygen to the bacteria in close proximity.

Ista Hydra Bio Sponge Filter

The filter removes excess food, decaying organic matter, free-floating particulates and dangerous chemicals. It prevents ammonia and nitrate amounts from exceeding to dangerous levels.

2. Biotic Factors

Zooplankton

Zooplankton was brought into the tank from the addition of mud from the fisheries pond. Parasitic worms, called Branchiobdellida, are found on the crayfish’s back and in the mud surrounding the rocks in the tank (Blue Crayfish FAQ).

Ghost Shrimp

Crayfish consume zooplankton, insects and other vertebrates and one another. Ghost shrimp were put into the tank as a food source for crayfish.

Snails

These can be eaten by crayfish for protein and calcium (from shells). The snails also consume algae. The ecosystem needs some algae, but not too much, so the snails will limit the algae growth. Two large inca snails were added to the tank. There are also several small snails that have emerged from the mud from the fisheries pond.

Beetles

Beetles were introduced into the tank ecosystem with the soil from the pond. These aquatic beetles are a member of the Agabus genus. The addition of these insects was inadvertent but can potentially benefit the system. The beetles serve as yet another heterotrophic component. They are an extremely abundant part of the natural crayfish ecosystem at the fisheries. They will eat the plants and serve as a food source to the crayfish.

Plants

The plants chosen were Duckweed and Ludwig. These consume the carbon dioxide that is produced by the crayfish's respiration and produces oxygen for the crayfish to consume. It assimilates nitrate and turns it into proteins that are consumed by the crayfish. An unknown submerged third plant is added and noted below the materials list.

Algae

Filamentous algae is important because it works as a food source for the crayfish. By eating the algae, the crayfish are converting a product of the algae to protein for the crayfish. Also, algae feed off the wastes produced by the crayfish. In other words, by eating the algae, the crayfish are converting a product of limited dietary use (the algae) to a product of many dietary uses (the protein of the crayfish). In turn, the algae absorb the wastes produced by the crayfish, and the cycle continues. This algae also will be eaten by the shrimp and snails to provide energy for the food chain of the ecosystem.

The specific algae that was chosen was Batrachospermum, which is a freshwater algae that has long, branched, threadlike filaments bearing dense whorl of branchlets, resembling beads on a string. This will make it easy for the crayfish to obtain these particles. The algae requires low light level: 50 to 100 ft candles of fluorescent light or fluorescent light from the ceiling. The medium is Soil-Water and the optimum growth temperature is 22° Celsius.

MASS BALANCE

MATERIALS LIST

​Item #	​Item Name	​Supplier	​Category Number	​Unit Cost	​Unit	​Quantity	​Total Cost
1	Filamentous algae- Batrachospermum	Carolina	153515	8.10	1 tube	1	8.10
2	Ghost Shrimp	PetCo	1035860	0.49	1	6	2.94
3	Duckweed, living	Carolina	161820	7.95	100	1	7.95
4	Gold Inca Snail	Petco	127426	1.99	1	2	3.98
5	Ludwigia, Living	Carolina	162141	8.25	1	1	8.25
6	Zoo MED Hermit Crab Sand	Petsmart	36-5162596	2.99	1 2-lb bag	2	5.98
7	Top Fin Mini Aquarium Air Pump	Petsmart	36-5174806	8.99	1 pump	1	8.99
8	Ista Hydra Bio Sponge Filter – Size mini round (5 gallons)	Marine Depot	AZ83147	3.99	1 filter	1	3.99
9	Air Releaser Stone	Carolina	671794	1.30	1 stone	1	1.30
10	Top Fin Aquarium Silicone Airline Tubing	PetSmart	36-5098112	5.99	1 tube	1	5.99
11	Omega One Veggie Rounds fish food	PetSmart	36-17395	4.99	1 2-oz can	1	4.99
12	50 Watt Sun Lamp Bulb	Walmart	RCHG 1089	13.41	1	1	13.41
13	Lamp Holder	Walmart	0005027696585	9.97	1	1	9.97
14	Spring Water (5 gal total)	Kroger	082657500805	1.99	1-2.5 gallon	2	3.98
15	Petco Aquarium Sand	Petco	1428250	3.76	1 bag	1	3.76
16	Aquatic Submerged Plant	Petco	Unknown	9.99	1	1	9.99
TOTAL	$103.57**

*The above total does not include taxes or shipping costs.

MONITORING PLANS

We monitored several aspects of the tank daily. These included water quality parameters, temperature, dissolved oxygen, and pH levels.

Water Quality

Phosphate - High phosphate levels contribute to eutrophication and leads to unwanted rapid plant growth (YSI Inc, 2013).

Nitrite – A direct result of the nitrogen cycle and is toxic to fish and aquatic life if too high.

Nitrate – A result of the oxidation of nitrogen compounds (YSI Inc, 2013).

Ammonia – Results from the breakdown of nitrogenous and is common in waste.

Temperature

The temperature was monitored to ensure it is maintained between 65-77 degrees Fahrenheit, which is optimal for crayfish life.

pH

Crayfish thrive between slightly acidic to slightly alkali pH levels; 6.5 and 7.5. Monitoring pH allowed us to indicate excess carbon dioxide via respiration.

Dissolved Oxygen (DO)

The dissolved oxygen levels were monitored to determine the efficiency and success of our microcosm. Aquatic plants increased dissolved oxygen levels through the process of photosynthesis, while the living organisms consumed the oxygen. If the DO level was to fall below 1 ppm, corrective action would have been taken to add oxygenated water.

Tank Feature Layout

The features in the tank were arranged in a certain way. The tank is an ecosystem in which the crayfish should interact with the features and feel relaxed. Stress on the crayfish will certainly deteriorate its health. If the ecosystem does not replicate what the crayfish is used to in its natural environment, then it will suffer from stress.

The pile of rocks on the end of the tank provide shelter. A small cave was made by positioning the rocks. The hideout for the crayfish was arranged so that the light source was not shining through the entrance. The hideout is dark and makes the crayfish feel safe, which will reduce stress. Most of the crayfish’s time was spent in the rocks; it came out to feed periodically. Crayfish typically burrow deep into the ground and build chimneys out of mud. However, when rocks are present the crayfish has sufficient shelter and did not need to burrow. The sand mixture in the bottom of the tank is one and a half inches deep. The crayfish was not able create an underground tunnel system, but it had enough soil to cover its body. The soil is necessary for the root structures of the two aquatic plants.

The plants are located on the end of the tank opposite from the shelter. The plants received light from an external lamp directed on that corner of the tank. The plants need the light more than any other feature in the tank. Having the light source located the maximum distance away from the shelter will reduce stress on the crayfish.

The system was designed to include an air gap of 2 to 3 inches. Air naturally contains more oxygen than the water. Therefore, the air portion of the tank acts as a storage of oxygen for the tank. The air pump pushed air from the top of the tank into the water. An airstone placed at the end of the airline was used to efficiently increase the dissolved oxygen in the tank. The pump was used to take advantage of the oxygen produced by the plants in the air portion of the tank. The airstone was located in the center of the tank and near the rocks. The area near the airstone obviously had the highest dissolved oxygen content in the tank. For this reason, the airstone was kept near the rocks where the crayfish spent most of its time. The aeration also helped to circulate the water.

Plants

The variety of plants in our system has attributed to our success. The motivation behind using different types of plants was to test the effectiveness of each variety. We did not want to put all our faith into one type of plant. The reaction of plant species to the microcosm environment is somewhat unpredictable. An algae film developed on the sides of the tank. This film supplemented the oxygen production from the plants placed in the tank.

The duckweed did function well in the system. This floating plant did not seem to produce enough oxygen, even when it covered entire surface of the water. The duckweed also created a barrier between the air and the water in the tank. A barrier can block the diffusion of oxygen into the water. Bacteria flourished on the root systems of the duckweed. Due to these negative effects, most of the duckweed was removed from the tank.

Ludwig was initially added to the tank. This plant may have produced oxygen at a better rate than duckweed, but the crayfish cut the Ludwig off at the root. All of the Ludwig died before the first test closure.

Dwarf hairgrass (Eleocharis acicularis) was added to replace the Ludwig. The crayfish was unable to cut this plant as much because it’s much tougher. The dwarf hairgrass functioned well, but the oxygen produced from two of these plants was not enough to support the system. Dr. Jim Stoeckel of the Auburn University Fisheries Department recommended the use of aquatic plants from the ponds of the E.W. Shells Fisheries Center. 40 grams of dwarf hairgrass was added to the system after the first test closure, bringing the total weight to 65 grams. Both the Ludwig and dwarf hairgrass are rooted aquatic plants. The crayfish is capable of killing rooted plants because it has access to the roots. A large floating plant can provide oxygen to the system without being too vulnerable to the crayfish. 40 grams of alligator weed (Alternanthera philoxeroides) was added to the tank. This plant floats and is very common in pond systems where crayfish live. The alligator weed proved to be the most valuable plant. Oxygen production increased by the greatest factor when this plant was added. OXYGEN INCREASE# The total wet mass of all plants used in the system was 105 grams. The oxygen production in the system was greatly increased due to the addition of the plants from the fisheries pond. The increase in oxygen production allowed the microcosm to stabilize the producer and consumer cycles.

Closure

The lid was designed simply with the intention of reducing the possibility of leaks. The lid fits in the lip on the top of the tank. The water extraction tube fits in a ¼” hole in the center of the tank. This hole is close to the rocks where the crayfish will spend most of its time. Knowing the quality of the water closest to the crayfish is important. The water extraction site is also across from where the pump is aerating the water. The site should have water that is well mixed. The pump was secured to the lid with coarse wire. Three holes in the lid hold the wire. The pump was originally placed on a shelf that was secured inside the tank with adhesive. The adhesive lost its ability to hold the shelf due to the moisture in the tank. The air pump fell into the water causing its electrical circuit to short. The pump was replaced. The newest setup is more secure and does not put trust into adhesive. The electrical cord for the air pump exits the tank through the slot.

Water was extracted from the tank using a syringe. Before the syringe was removed from the water extraction tube, the tube was pinched closed. Removing significant quantities of water for testing can create a vacuum. In order to avoid a vacuum being creating, an aqua lung was attached to the tank. The aqua lung is essentially a plastic IV bag that will was used as a side storage of water for the tank. After sufficient water was removed from the system, the tube from the aqua lung was opened. Water was allowed to enter the system until the extracted water was replaced by approximately the same volume. This method was practiced in order to not prevent any mass from crossing the boundary of the system. Plumber’s putty was used to seal the all openings and the four edges of the lid. The plumber’s putty creates an acceptable seal but is malleable enough to be removed easily. This sealant provided a better seal than silicone caulk. The ability to remove the lid easily helped in making changes to the system after the test closures.

Behavior

When first introduced to the system, the crayfish spent the majority of its time hiding in the rocks. The crayfish was mostly stationary as it acclimated to the new environment. During the third week the crayfish was in the open microcosm, it molted. Abnormal behavior was observed for a week before this occurrence. The exoskeleton became lighter in color. The crayfish also seemed to be constantly rubbing its shell with its appendages. After molting, the crayfish became noticeably smaller in size and darker in color. Its behavior became more reclusive. The soft exoskeleton of the newly molted crayfish made it more vulnerable, so it found safety hiding deep within the rocks. The water hardness was greater than or equal to 120 ppm for the entire time the crayfish was in the tank, which is greater than the acceptable level of 50 ppm. The photoperiod is thought to have initiated the molting process. The crayfish regenerated its shell within a week after molting. It appeared healthier and more active.

The addition alligator weed to the system seemed to be enjoyed by the crayfish. An increase in food and oxygen visibly improved the crayfish’s health. The addition of more plants was the turning point in the success of the system. The health of the crayfish improved as the system was able to stabilize.

The crayfish did not eat any of the other invertebrates in the system. Snails and water beetles were the other invertebrates in the tank. The crayfish was not expected to eat the large snails placed in the system, but it also did not eat the small snails that developed. The water beetles and the crayfish had no interaction. The crayfish had enough food available from the plants and did not need to kill the invertebrates for food.

The crayfish molted for a second time during the week-long closure. The reason for the second molting is unclear. The light period was reduced from 24 hours per day to 16 hours per day. The increase in dark hours was thought to discourage molting. However, the crayfish molted twice during a 7 week span. The behavior of the crayfish did not change after the second molt. It appeared to be just as healthy and active as before it molted.

Bacterial Growth

The microcosm experienced an overpopulation of bacteria during the beginning stages of this experiment. The tank originally contained a gallon of pond water. The tank had a 1 to 5 pond water to spring water ratio. 1.5 kilograms of pond sediment was also added to the system. The large amount of pond water and sediment was added to the system to jumpstart the bacteria and nutrient cycles. The addition of organisms and nutrients from the pond was intended to replicate what occurs in a natural pond ecosystem. The thought was that if these processes occur in the pond then they should occur in the same water and sediment if it is contained in a microcosm. This theory did not prove true. The nitrifying bacteria introduced to the system quickly became overabundant due to its new environment. The bacteria feasted on the sediment which had a high organic matter content. The warm and still water provided an optimal growing environment for the bacteria. The oxygen in the microcosm was rapidly consumed by the bacteria. During the first test closure, the dissolved oxygen content of the water dropped from 7.86 ppm to 1.9 ppm in just 24 hours. To combat this major problem, the water was changed and the tank was thoroughly cleaned. The rocks were scrubbed and the soil was baked at 105°C for 24 hours. The water was replaced by pure spring water. We believe that inoculating the tank with bacteria is beneficial, but we introduced too much bacteria and organic matter. The small scale system can be sufficiently inoculated with a much smaller amount of pond water. We did not add more pond water after we cleaned the tank. However, we believe that enough bacteria remained in the tank after cleaning to repopulate the tank in much smaller numbers.

SETBACKS AND FAILURES

We added 0.2 gallons of natural pond water and dirt in order to incorporate nutrients that exist in the crawfish’s natural environment. The water and mud was taken directly from the same pond as where the crawfish were captured. The ratio of spring water to pond water was 5 to 1 gallons so as make sure the majority of the water was clean and clear. We anticipate that these added nutrients from the existing pond will jumpstart natural processes within our microcosm. Processes like plant growth, nitrogen cycling, algae growth and zooplankton growth will both be assisted by these additions. The increased organic matter in the mud will spark and continue plant growth. The dead organic matter collected with the mud will supply the bacteria needed to convert nitrogen in the nitrogen cycle. Algae growth and zooplankton will also utilize those microbes from the pond water for survival (YSI Inc, 2013).

THIS DID NOT WORK BECAUSE… THE SPONGE FILTER … DUCKWEED.

Sponge Filter- made more algae

Duckweed- stuck to the sides of the tank so when we drew water to take samples, it would dry up and die. Also, when we cleaned the tank a lot of it disappeared.

FINAL DATA SHEET DESIGN

CONCLUSION

WORKS CITED

Pohl, Kathleen, and Jun Nanao. Crayfish. Milwaukee: Raintree, 1987. Print.

“Crawfish Production Manual.” Chapter 7. Water Quality and Management (n.d.): n. pag. Lousiana State University Agriculture Center. LSU AgCenter, 2014. Web. 31 Aug. 2014. <https://www.lsuagcenter.com/NR/rdonlyres/6613CCA1-C0F9-45EF-8160-76FD42459291/34043/Chapter7CrawfishProductionWaterQualityandMgmt.pdf>.

Hand, Rado. "Online Gallons in Beach Sand per 1 Gram Unit Converter." Beach Sand Conversion. Traditional Oven, 2013. Web. 06 Oct. 2014. <http://www.traditionaloven.com/building/beach-sand/convert-gram-g-beach-sand-to-gal-of-beach-sand.html>.

Seyffarth, Keith. "What Does My Filter Do?" - The First Tank Guide. Keith Seyffarth, 2012. Web. 06 Oct. 2014. <http://www.firsttankguide.net/filters.php>.

Helms, Brian. "Crayfish Biology, Ecology, and Conservation." Interview. AU Natural History Museum, Auburn University 12 Sept. 2014: Print.

Owens, Jace, John Rains, Manjinder Kaur, and Mehdi Rexaeianzadeh. Research Report 1. Rep. Auburn: Auburn U Biosystems Engineering, 2014. Print.

"Blue Crawfish FAQ." FAQ. Blue Crayfish, n.d. Web. 07 Oct. 2014. <http://www.bluecrayfish.com/bcf-faq.html>.

YSI Incorporated. "YSI Inc | Water Quality Sampling and Monitoring Meters for Dissolved Oxygen (DO), PH, Turbidity." YSI Inc. Xylem Inc., 2013. Web. 07 Oct. 2014. <http://www.ysi.com/index.php>.