REPORT: BIORB AQUARIUM PROJECT

Transcription

1 Fish Disease Research Unit Department of infectious diseases University of Veterinary Medicine Hannover Bünteweg Hanover Germany Tel: +49(0)511 / Fax: +49(0)511 / REPORT: BIORB AQUARIUM PROJECT Report: biorb aquarium project - 1 -

2 Index Summary 1 Introduction 2 Under water optics 3 Water quality 4 Behaviour 4.1 General behaviour 4.2 Feeding behaviour 5 Conclusions Appendices Appendix I: oxygen and temperature measuring points Appendix II: data water parameters Appendix IIa: oxygen Appendix IIb: temperature Appendix IIc: nitrogen and ph Appendix IId: hardness Appendix III: ph Appendix IV: nitrate Report: biorb aquarium project - 2 -

3 Summary This report compares two biorb aquariums (30L and 60L) with a commercially available 60L rectangular aquarium. BiOrb aquariums are spherical. Under water optics were done to investigate possible distortions due to aquarium shape. Possible effects of aquarium design (shape and filter system) on fish welfare were investigated by testing oxygenation, water quality and behaviour. Aquariums were observed over a time period of three months, where each 28 days new fish coming from a rectangular aquarium were added. Aquariums were tested under stressed conditions (too many fish, too much food, no water exchange) to mimic worst case customer behaviour. All aquariums were treated equally In the underwater optics no distortions were found in the biorb aquariums. In the rectangular aquarium reflections could be observed. Oxygenation in all aquariums was good. Oxygen concentrations and temperature were stabile throughout the aquariums. In the first two months nitrite and ammonium peaks were measured in all three aquariums. The peaks were higher in the biorb aquarium than in the rectangular aquarium. However, fish did not show altered behaviour or indications of disease. After the first two months ammonium and nitrite had decreased to low levels and stabilised. The rectangular aquarium was less stable concerning ammonium in the third month. No critical values were observed throughout the experiment for any of the aquariums for carbonate and total hardness, as well as ph and nitrate. After transfer to the biorb-aquariums fish needed a couple of days to adapt to their new environment. After the initial adaptation fish acted calm and fed well. Fish in the rectangular aquarium needed only half a day to get adjusted and were more conditioned to food. In this experiment, testing oxygenation, optics, behaviour and filtration no indications were found that biorb aquariums (60L and 30L) are any less fish friendly for free swimming fish than standard rectangular aquariums. Between the 60- and 30L-biOrb-aquarium no clear differences were found in regard to fish welfare or stability of the system. Report: biorb aquarium project - 3 -

4 1 Introduction This report evaluates a project conducted by the Fish Disease Research Unit, Department Of Infectious Diseases, School of Veterinarian Medicine Hanover, Germany. The project was conducted for ReefOne, manufacturer of biorb aquariums and compared two biorb aquariums (30L and 60L) with a commercially available 60L rectangular aquarium (MP). BiOrbs are spherical with an integrated filter, aerator and artificial lighting. Underwater optics were conducted, water parameters were monitored and general behaviour as well as feeding behaviour of the fish were observed. All aquariums were placed and treated under the same conditions. To the rectangular aquarium commercially available pebble-sand, a standard 60L heater (JÄGER) and filter system (EHEIM) were added. To the biorb aquariums standard biorb ceramic media was added, the integrated ReefOne filter system was used and in each aquarium a heater provided by ReefOne was installed. The filters in the biorb-aquariums were not exchanged as recommend in the user manual, because this is not possible for the rectangular aquarium (washing the filter material of the rectangular aquarium would be possible but not advisable). To all aquariums artificial plants - provided by ReefOne - were added. The aquariums were filled with untreated (tap) water and were left to rest for a day, after which the first Platys (Xiphophorus maculatus) were added. Additional fish were added each 28 days (fish were added on day 1, 29 and 56 of the experiment). The total experiment lasted 81 days. To both 60L aquariums each time eight Platys were added (recommended are six). After two months, the maximum stocking load of 24 small tropical fish was reached. To the 30L aquarium each time four Platys were added (only three is recommended). After two months the maximum stocking load of twelve small tropical fish was reached. Each day the same amount of food was added per fish (four pellets of Hikari Staple floating type per fish). The pellets used in the study was larger than the pellets provided by ReefOne for tropical fish (Hikari Tropical micro pellets). This way food could be quantified and so an equal nutrient addition was obtained for each fish. Due to larger pellet size more food was added as recommended in the user s manual. This can lead to a larger nutrient load. Excess food was removed after ten minutes (if necessary). Report: biorb aquarium project - 4 -

5 2 Under water optics Under water optics were taken with a SONY 5.0 Megapixel Cybershot digital-camera (with Sony 40m Marine Pack). The under-water-optics included pictures as well as video sequences. For the biorbs (both 30L and 60L) four different camera positions were set; at ca. 50% of aquarium height and 50% of aquarium width at ca. 50% of aquarium height and 5 cm from glass at ca. 75% of aquarium height and 50% of aquarium width at ca. 75% of aquarium height and 5 cm from glass For the rectangular aquarium we used two locations: in the centre of the aquarium 5 cm from the short side of the aquarium From each location pictures were taken towards all corners and straight towards short and long sides of the glass. Short video sequences were made of each aquarium to get a better impression of the fish s view whilst swimming in the aquarium, because the fish s view to the outside might change by moving around the aquarium. In total eight pictures and one video sequence for biorb-30l-aquarium, nine pictures and one video sequence for biorb-60laquarium and 13 pictures and one video sequence for rectangular-60l-aquarium were taken. All three aquariums were set up and placed on a table in the middle of a room and were filled up with untreated tap water. No plants or decoration were added during the under-wateroptics, filter and aquarium-lighting were not switched on. The eyes of fish are profoundly different from the eyes of most other vertebrates, since fish continue to grow throughout life and because they see underwater (different light refraction). Furthermore, fish eyes show many more variations than terrestrial animals, because of the variety of light regimes in which they live. In order to properly evaluate the under-wateroptics results, we therefor need to understand the anatomy and physiology of a fish s eye. Unlike our eyes in which we monitor a rather limited part of our surroundings at any one time a fish can probably see some parts of the environment with binocular vision and other parts, to the side with lateral vision using each eye independently. Report: biorb aquarium project - 5 -

6 Fish also have an inflexible neck which may require modifications of the eye to ensure a wide binocular visual field in which there is overlap of the images of the outside world in each eye. In contrast to land animals, refraction in fish s eyes does not take place in the cornea, but in the lens. Fish accommodate by changing the distance between the lens and the retina. In most fish there is a switch in the eye from dim light to bright light. This light or dark adaptation takes 20 to 30 minutes. These adaptations of the fish retina are not found in terrestrial animals where rapid changes in pupil diameter play an important role in controlling the amount of light entering the eye. Most fish have a duplex retina like ours, i.e. one containing both rods and cones. Cones of fish contain three to four different pigments. The presence of two pigments is an advantage in detecting reflected light, since this usually has a slightly different spectrum than the original light. * In both spherical aquariums (biorb-30l and biorb-60l) we had good visibility from all positions, both inside the aquarium and to the outside of the aquarium. Also the video sequences show a clear view without losing orientation. No distortions of images from the outside of the aquariums could be seen. The above generally applies to the rectangular aquarium. However the video sequence clearly shows a reflection and an overlap in the view from the short and from the long side of the aquarium. * Taken from: Biology of fishes, Bone, Q., Marshall, N.B. and Blaxter, J.H.S. (2 nd ed,), Blackie Academic & Professional, Suffolk Report: biorb aquarium project - 6 -

7 3 Water quality Water parameters of the unstocked aquariums were measured 24 hours before and directly before adding the first fish. No clear effects on water quality by waiting a day before adding the fish could be observed. Water quality parameters were then measured for stocked aquariums. Parameters which were measured three times a week were: - oxygen (mg/l) - temperature ( C) - ph - nitrate (mg/l) - nitrite (mg/l) - ammonium (mg/l) Total hardness and carbonate hardness ( dh) were measured once a week. Oxygen and temperature were measured at four different locations in the aquariums (appendix I). For all other water parameters a water sample was taken. If the water level in one of the biorbaquariums was less then 5 cm above top of aeration tube, then all aquariums were filled up with untreated tap water. The welfare of the fish was observed daily. Because no change in behaviour or food uptake could be observed it was decided not to change the water. However some parameters arose to a merit considered to be bad for fish on a long term basis. Data of the water parameters can be found attached to this report (appendix II). In general it can be stated that some parameters rose above the advised welfare limit. Still no change in behaviour or food uptake could be observed. The values for total hardness and carbonate hardness correspond with the standard of the local tap water. They were stable within minor deviations. Addition of fish leads to an increased gas exchange which leads to a rise of the CO 2 and therefore also a rise of the H 2 CO 3 in the water body according to equation 1. Equation 1: H 2 O + CO 2 H 2 CO 3 HCO H + CO H + (ph-dependent). Report: biorb aquarium project - 7 -

8 This leads to a rise of the HCO - 3, which is mostly present as calcium-dihydrogencarbonate. Calcium-dihydrogencarbonate can be measured as carbonate hardness. A short rise of carbonate hardness was expected after the addition of fish. However, this rise was not noticed, because hardness was only measured once a week. Furthermore, an increased nitrite amount could be observed after the introduction of additional fish (especially in the biorb-aquariums). This can be explained by a rise of ammonium which increases the activity of the nitrifying bacteria: Equation 2: NH O 2 nitrifying bacteria NO H +. The additional acid is able to lower the carbonate hardness and to keep a higher amount of CO 2 dissolved. In all aquariums a drop of carbonate hardness was observed (figure 1). Between day 40 and day 60, this drop was more pronounced in the rectangular aquarium. 18 Hardness dh dkh biorb 30L dkh biorb 60L dkh rect. 60L dgh biorb 30L dgh BiOrb 60L dgh rect. 60L day Fig. 1: Total hardness ( dgh) and carbonate hardness ( dkh) of the biorb-aquariums and the rectangular 60 L aquarium The ph showed very little deviations. This can be explained by the calcium-carbonic acidequilibrium. Dissolved calcium buffers acids in the water: Equation 3: H 2 CO 3 + CaCO 3 Ca(HCO 3 ) 2. Report: biorb aquarium project - 8 -

9 The stabilisation of the carbonate hardness to the starting values is caused by the calcium and its reaction with the carbonic acid to bicarbonate. The addition of fish on day 1, 29 and 56 appears to have no or little influence (not measurable) on the ph values (appendix III). However an increased ammonia value was found for all aquariums which decreased over time with maturation of the aquariums. The addition of fish did not have a large influence on the oxygen concentrations. All three aquariums were well oxygenated and showed very similar deviations throughout the experiment (appendix IIa). The rectangular aquarium showed no clear differences between the different measuring points (appendix I and IIa). For the biorb-aquariums slight differences were measured at some time-points (appendix IIa). Towards the end of the experiment the aeration pump was stopped several times. Consequently, the fish were found swimming near the water surface. Fish returned to normal behaviour quickly after the aeration pump was started again. No clear differences were found in the oxygen concentrations. In general the oxygen concentrations in the 60L-biOrb-aquarium were higher than in the 30L-biOrbaquarium. The oxygen concentrations in the biorb-aquarium were higher than in the rectangular aquarium. The oxygen concentrations in the biorb-aquarium were probably higher due to the vigorous aeration and turbulence. This keeps the gases in equilibrium with the air above the water surface. This cased the gases to be well distributed and redundant gases to be easily expelled. No clear differences in any of the aquariums could be found in temperature between the different positions in each aquarium. After two to three days the temperature in the rectangular aquarium stayed steady between 24.5 and 25.5 C. This is the temperature recommended for Platys such as used in the experiment. In the 60L-biOrb-aquarium the temperature stayed steady between 24 and 25 C after day 17 (except for two deviant values). The temperature in the 30L-biOrb-aquarium dropped from 25 C to 23 C on day 31. During the next days there was a steady decrease of the temperature from circa 23 C to 22 C, and eventually to 21.6 C on day 46. The heater appeared to malfunction so the heater was exchanged with a standard commercial one. After this exchange the temperature rose again to 23 C and stayed stable. The type of heater used in this study is no longer available and meanwhile has been replaced by a new model. Report: biorb aquarium project - 9 -

10 Fish excrete their nitrogen waste products as ammonium, and not as urea which is less toxic as ammonium. Fish can produce ammonium, because it is easily diluted in water. When the ammonium concentration in the water becomes too high, fish cannot excrete their ammonium and will die due to self-toxication. Nitrogen can be present as ammonium (NH + 4 ) or ammoniac (NH 3 ). At neutral ph, NH 3 is present at a ratio of less than 1 %. With increasing ph, the equilibrium between ammonium and ammoniac shifts towards the highly toxic ammoniac. Filter bacteria can catabolise ammonium into nitrite. Nitrite is less toxic as ammoniac. However, first a bacterial biofilm on filter materials has to be established. Nitrite can be catabolised by other bacteria in the same biofilm to the even less toxic nitrate. Over time several peaks of ammonium were observed in all aquariums (fig. 2). In the two biorb-aquariums a small ammonium-peak was followed by a high nitrite-peak after the first addition of fish (day 16-26). Nitrite reached very high concentrations of up to 2.0 mg/l, which can be toxic for fish over a prolonged period of time. After this the nitrite concentration decreased to detection limit of the test. It rose no further and stayed stable due to the matured bacterial load in the aquariums. However, ammonium ascended again (day 35) after the second addition of fish. In the experiment the fish were not harmed by the high concentrations, this was due to good health and condition. Such high concentrations should be avoided. Fish weakened due to sickness or transport-stress (after buying fish) cannot handle these high concentrations and can be impaired. In general biological filter systems need four to six weeks to establish a mature bacterial community, which is needed to catabolise fish excrements. After six weeks no further rise of ammonium or nitrite could be observed for the biorb-aquariums. Even the third addition of fish did not have a measurable impact on nitrogen levels. The water biology seemed to have reached a stable stage (figure 2) and after the initial maturation period the biorb filter system seems to diminish the nitrogen load reliably. In the rectangular aquarium a rise of nitrite and a simultaneous rise of ammonium could also be observed after the first addition. However the rise of ammonium was smaller for the rectangular aquarium as for the biorb-aquariums. Nitrite stayed below 0.1 mg/l which is said to be upper limit to be tolerated well by fish. Ammonium concentration rose before the second addition of fish. A few days after the second addition ammonium started to decrease again. Several further peaks could be observed after the third addition of fish. This might indicate that the filter has reached its maximum capacity. Report: biorb aquarium project

11 Still ammonium stayed below 1 mg/l during the whole experiment (figure 2). These concentrations clearly lie below those of the biorb-aquariums, but can still impair fish. All three aquariums showed a steady increase in nitrate. The highest value was found for the rectangular aquarium (appendix IV). The nitrate concentration did not reach critical values. 2,0 Nitrite (NO 2 - ) & ammonium (NH4 + ) BiOrb 30L BiOrb 60L rect. 60L 1,5 mg/l 1,0 0,5 0, days days days NH 4 + NO 2 - Fig. 2: Nitrite and ammonium of 30L- and 60L-biOrb-aquariums and 60L rectangular. aquarium (arrows indicate the addition of fish) It should be considered that more than the recommended amount of food was added and no water was exchanged throughout the experiment which means stress conditions for both fish and filter bacteria. If water exchange had been made ammonium/nitrite would not have reached such high levels. In general it is recommended that aquarium-owners exchange 10% of water once a week. Water exchange is especially important during the first weeks after setting up an aquarium, because of lacking filter capacity. ReefOne recommends 30% water exchange every four to eight weeks. Evaluating the water parameters (nitrite, nitrate and ammonium) of the biorb-aquariums it is advisable to do weekly water exchange during the first four weeks. After this period the recommendation of ReefOne can be followed. Although more fish (per month) were added to the aquarium as recommended by ReefOne, fish health was not impaired. Report: biorb aquarium project

12 4 Behaviour 4.1 General behaviour The following general behavioural observations were made two times a day (morning, afternoon before feeding), three times a week: - swimming direction - placement in water body - speed/calmness - shoaling behaviour - use of hiding places - general other observations All fish showed changed behaviour directly after placement in the aquarium. However the fish in the rectangular aquarium returned to their normal behaviour within half a day. Food uptake at the first feeding was good. The fish in the biorb-aquariums hid in the back of the aquarium and behind the plants, near to the bottom. Furthermore, they hardly left their hiding places around feeding time. These fish returned to their normal behaviour after approximately one week. The fish in the 30L-aquarium adjusted to the spherical aquarium somewhat slower than those in the 60L-aquarium. In a mild form these actions were also observed after adding the second and third groups of fish. All fish came from rectangular aquariums. It can be assumed that the fish therefore needed more time to get adjusted to their new spherical surroundings. After the first week no distinct differences in behaviour could be observed between the different aquariums (except for feeding behaviour, see page 14). The fish in the rectangular aquarium were food-fixated and came to the front as soon as a person entered the room. In general the swimming behaviour can be described as mixed in all aquariums which means fish were found in all locations of the aquariums. The fish in the biorb-aquariums had a tendency to swim more often at the top of the aquarium. Under natural conditions platys usually swim near the water surface because they feed on insects on the water surface. It is not possible to make an exact description of the swimming behaviour of all fish, because the fish were seldom in one shoal and because the fish changed their position in the aquarium regularly (figure 3, 4, and 5). Report: biorb aquarium project

13 Position of fish in aquarium 40 biorb 30L biorb 60L rect. 60L b f b 0 front back top bottom middle mixed Fig. 3: Position of fish in 30L and 60L biorb-aquariums and rectangular 60L aquarium Platys are fish, which tend to build groups. Unstressed fish also leave the group. In all three aquariums fish were found both swimming solo and in groups (figure 4) Shoaling behaviour biorb 30L biorb 60L rect. 60L number of observation solo shoals dispersed Fig. 4: Shoaling behaviour in 30L and 60L biorb-aquariums and rectangular aquarium Report: biorb aquarium project

14 35 30 biorb 30L biorb 60L rect. 60L Swimming behaviour number of observation front back top mixed across static Fig. 5: Swimming behaviour of fish in 30L and 60L biorbs and rectangular 60L aquarium Due to the shape of the biorb-aquariums it is impossible to overview the complete aquarium at once. To see all areas of the aquarium one has to move around the aquarium. When a biorb-aquarium (30L or 60L) is placed close to a wall it is hard to observe the fish and judge their health, when they are not in the front of the aquarium. When decorated equally a fish s corpse is therefore more likely to go unnoticed in a biorb-aquarium as in a rectangular one. However rectangular aquariums tend to be decorated more and therefore also have corners in which fish can be overseen. All fish appeared healthy and no signs of injury were observed throughout the experiment. No aggressive behaviour was observed in any of the aquariums at any time. In both biorbaquariums the platys reproduced. Report: biorb aquarium project

15 4.2 Feeding behaviour The following behavioural observations were made daily around feeding time (once a day): - time till food uptake - behaviour during feeding time - food uptake The behaviour during feeding time was peaceful in all aquariums. In the rectangular aquarium the behaviour of the fish before feeding was different from the behaviour of the biorb-fish. As soon as the fish in the rectangular aquarium observed a person entering the room they directly swam towards the front in anticipation of. The fish in the 30L-and 60L-biOrbaquarium did not show such a clear reaction nor any obvious differences in their behaviour. The fish in the rectangular aquarium show conditioned behaviour whereas the biorbaquarium-fish do not. This probably, because fish do not notice the impact of food on the water surface as water tension is different due to the different water circulation. In the biorb aquariums it was observed that after adding the pellets they directly drifted towards the margins of the aquarium water surface. This made the food uptake difficult for the fish. Furthermore it was observed that the biorb fish did not directly swim towards the food. It can be assumed that the impact of the pellets on the water surface was less noticeable for the fish, due to the disturbance of the water tension by the bubbles of the oxygenation tube. This problem could be solved by putting the pellets into a feeding ring. Because larger pellets as recommended for tropical fish were used, the fish in all three aquariums were not able to swallow the pellets down in one piece. The fish left the pellets to soak in the water long enough for the pellets to soften so that they were able to nibble pieces of the pellets. It is a disadvantage when food pellets are left in the water body for a prolonged period, because nutrients are withdrawn by diffusion. This might lead to unnecessary water pollution and in the long run to nutrient deficiency in the fish. Therefore pellet size should be adjusted to fish size. Platys, kept in an additional rectangular aquarium, were fed with Hikari Tropical micro pellets, provided by ReefOne. These pellets are of a smaller size than the Hikari Staple floating type and were well accepted by the fish. The pellets were taken up directly by the fish, and swallowed in one piece. The disadvantage of such small pellets however, is that an exact quantification of pellet amount is impossible. Therefore an excessive food dose is likely to happen which can also happen with other kinds of commercially available fish food. Report: biorb aquarium project

16 5 Conclusions The view from the biorbs to the outside world is clear and undistorted. The main difference in optics between the commercially available rectangular aquarium and the biorb aquariums seems to be the reflections in the rectangular aquarium. These reflections are confusing to the human eye. It is unclear how reflections are perceived by fish. There are no indications that the spherical form of the biorb aquariums has any disadvantages with regard to the fish s vision. In all aquariums a maturation of the water by an increase of filter bacteria was found, as is know from literature. The rectangular aquarium showed a slightly faster maturation than the biorb-aquariums. Nitrite did not reach as high concentrations in the rectangular 60Laquarium as it did in the biorb-aquariums. Ammonium showed one short, very high peak in each of the biorb-aquariums. However, in general no major differences could be observed. Although some water quality parameters (ammonium and nitrite) arose to a merit considered to be bad for fish on a long term basis, no change in behaviour or food uptake could be observed. If a water exchange would have been made according to the biorb manual the nitrite levels would have been reduced to a level which would not be harmful to fish even on a long run. All fish came from rectangular aquariums and were then transferred to the experimental aquariums. After the transfer to the biorb-aquariums the Platys behaved differently. They hid in plants and preferred the bottom of the aquarium. However they adapted and returned to normal behaviour after one week. It can be assumed that the fish therefore needed more time to get adjusted to their new spherical surroundings. After the first week behaviour of the fish in the biorb aquariums was still slightly different from fish in the rectangular aquarium. The fish in the rectangular aquarium were more active and food fixed. The fish in the biorbs were very calm and not easily disturbed by influences from the outside and fed well. In summary, in this experiment testing oxygenation, optics, behaviour and filtration no indications were found that biorb aquariums (60L and 30L) are any less fish friendly for free swimming fish than standard rectangular aquariums. Between the 60- and 30L-biOrbaquarium no clear differences were found in regard to fish welfare or stability of the system. Report: biorb aquarium project