La Azotea – La Jaula, small tributary of Rio Paraná, in Pre-Delta National Park, Entre Rios, Argentina
_th place in Biotope Aquarium Design Contest 2020
Volume: 184,8 L
Dimensions: 100x42x44 cm
List of fishes: Fauna = Aphyocharax anisitsi (15), Apistogramma borellii (6), Corydoras hastatus (11), Corydoras paleatus (10), Hyphessobrycon eques (14), Otocinclus arnoldi (9), Phalloceros caudimaculatus (6), Rineloricaria parva (2) and Palaemon argentinus (4)
List of plants: Flora = Echinodorus grandiflorus, Eichhornia sp., Eleocharis sp., Gymnocoronis spilanthoides, Juncus sp., Myriophyllum aquaticum, and the floating plants: Limnobium laevigatum and Pistia stratiotes
Description of decorations: Decorations = Fine river sand, wood, small roundish rocks, dry leaves and botanicals (like, for example, Jacaranda mimosifolia seed pods, a sub-tropical tree native from Argentina) caught in nature
Description of equipment: Filtration = Seachem – Tidal 75, with an adjustable flow, that can arrive till a maximum of 1500 L/h, that I only used in the period that I tried to simulate the rainy season. Because in the dry season the flow is always less strong. It is important to note that this canister filter works with biological filter material
Lightning = Chihiros E-series RGB90, with a variable photoperiod (dry season: 7h; rainy season: 10h), but as none of the species lives under bright daylight, for 10 hours, many parts of the aquarium are shady. I used driftwood and floating plants for that. And I dimmered the LED light, simulating a the natural daylight intensity
Water parameters: Water parameters = Even if, for most of the year, the temperature was between 19 ºC and 22 ºC, it dropped until 15 ºC, in some winter days, and reached 29 ºC in the summer. Slightly tea-color in the rainy season, and darker in the dry one. In the rainy season the water parameters measured were: GH = 6; KH = 3; pH = 7,24; NH4 = 0 mg/L; NO2 = 0 mg/L; NO3 = 10 mg/L; K = 8 mg/L; Fe = 0,1 mg/L; TDS = 138 mg/L; Condutivity = 263 uS/cm
Additional info: Interesting facts = In the dry season I only made a small (approximately 20%) monthly, water change and leave the aquarium water level lower. On the other hand, in the rainy season, I made weekly water changes of approximatly 40%, and add more dry leaves and botanicals, to try to simulate the periodic flood pulses.
To give some extra nutrients to the plants, and permit that they grow lusher, every 2 months, I put some fertilizer, Aquario’s NEO plants tab (Long lasting and Fe), in the ground. A good option for plants, that doesn’t change the water parameters, and consequently the fauna isn’t affected.
The bibliography shows that predominant soil texture is characterized, in general, by the predominance of the silt fraction. But has I found extremely difficult to maintain an aquarium with so small diameter particles, I opted to use river sand with a small size grain.
I didn’t use a heater, because the temperature differences, between the dry and rainy seasons, in this region of Argentina, are very similar with the portuguese ones. Making this project even more sustentable.
Lastly, as the portuguese ornamental fish market is very peripheral, it wasn’t easy to find many fish and plants species (some are considered invasive ones) that I wanted to use in this biotope. And some of them show a little colour/pattern differences, since the majority is (re)produced in captivity. Although they mantain, in the aquarium, the expected behavior they have in nature.
INFORMATION ABOUT BIOTOPE:
Description of the area surrounding the biotope: The Paraná river is the second biggest river in South America. It borns from the union of Grande and Paranaiba rivers and runs through Brazil, Paraguay, and Argentina for some 3,740 Km [1, 2].
It merges first with the Paraguay river and then farther downstream with the Uruguay river to form the La Plata river and empties into the Atlantic Ocean. During the part of its course downstream from the city of Diamante, Entre Ríos, it splits into several arms and it forms the Paraná Delta. 
The composition of the Paraná river is extremely high in sediment and includes approximately 25% clay sediments, which equates to about 45000 million tonnes per year of which, 15% is sand (25 million tonnes / year) and about 60% is silt (90 million tonnes / year). This large amount of suspended solids, mostly comes from the Bermejo river (originates in the Bolivian Andes), in the floodplain, it formed many mutating islands, over millions of years, even in spite of the interventions made my mankind. [1, 3, 4, 5]
So, it’s possible to affirm, that the flood plain of the Paraná river constitutes a wetland where the landscape is the result of continuous geomorphological and river processes that had place in the past and continue today. Because of its strategic location, it offers refuge, feeding, reproduction and breeding areas to different fish species, and constitutes an important place for the wide variety of living organisms that live in these waters. 
Pre-Delta National Park (PDNP) is located southwest of Entre Rios Province, on the left bank of the Paraná river, south of the city of Diamante, where the Paraná river forks in hundreds of meandering arms. It extends from 32º 03’ 43’’S and 60º 38’ 39’’W, with a surface of about 2600 ha. [1, 5, 6, 7, 8]
At its northwest limit we can find the tributary La Azotea – La Jaula (32º07’17.8”S/ 60º38’04.3”W). [1, 9, 10]
Description of the underwater landscape of the biotope: Analyzing the underwater morphology of this area, near the margin, we found that the predominant soil textures are characterized, in general, by the predominance of the silt fraction, with more variable clay and sand (small to medium size grain) concentrations, this fact makes the water cloudy, with little visibility. In addition, the periodic flood pulses promote the entry of suspended solids. It’s also possible to find some fine gravel and roundish rocks. And near the margin the water is slightly tea-color, with a slow flow, and normally some driftwood and dried leaf litter can be found. [9, 11, 12]
As told before, in this area, the morphology depends of the floods, that are usually very important and have an erosion effect, by sedimentation. For this reason, the relief, the depth and the transparency of the water change slowly and constantly. 
The climate of the region is temperate-hot and humid, with an average annual temperature of 19 ºC and 900 mm of annual precipitation. 
There is more precipitation in the warm season and it is much drier in the cool season, the large volume of water in the region contributes to the high humidity of 75%. This generates a low thermal amplitude and aids in development of an humid subtropical micro-climate. 
For the biotope aquarium that I made, as I decided to recreate a shallow water zone, near the margins of the small tributary La Azotea – La Jaula, where the water flow isn’t strong. I chose some of the smaller fish and invertebrates, that prefer to live protected by the floating vegetation, the network of roots, stems and leaves, and the dried leaf litter, driftwood and small rocks that stay accumulated there, like: Aphyocharax anisitsi (15), Apistogramma borellii (6), Corydoras hastatus (11), Corydoras paleatus (10), Hyphessobrycon eques (14), Otocinclus arnoldi (9), Phalloceros caudimaculatus (6), Rineloricaria parva (4) and some shrimps of the genera Palaemon argentinus (4). On the other hand, the flora I chose to recreate the biotope was: Echinodorus grandiflorus, Eichhornia sp., Eleocharis sp., Gymnocoronis spilanthoides, Juncus sp., Myriophyllum aquaticum, and the floating plants: Limnobium laevigatum and Pistia stratiotes.
Description of the parameters of the habitat: Even if the water parameters in the tributary La Azotea – La Jaula change seasonally, after a flooded period we can observe that it’s a relatively soft water, the pH is almost neutral, the total dissolved solids is about 56 mg/L, and has a conductivity of 79 uS/cm. The nitrite concentration is 0,01 mg/L, the nitrate one is around 0,25 mg/L, and the ammonium concentration is around 0,3 mg/L. The dissolved oxygen is 7,7 mg/L, and the total ionic concentration (where the bicarbonate ions (34 mg/L) have the biggest contribution for this value, followed by the chloride (10 mg/L), sodium (6,45 mg/L), calcium (6,4 mg/L), potassium (1,72 mg/L) and other ions (6,43 mg/L)) is around 65 mg/L. Finally, the water temperatures change from 15 ºC in the winter to almost 27 ºC in the summer season. [3, 9, 10, 14, 15, 16, 17, 18, 19, 20, 21]
List of fishes and invertebrates occurring in the nature biotope: The ecosystem of the PDNP, formed in the flooded area, has extremely diverse wildlife, providing habitats for 456 plant species, 256 birds, 185 fish, 30 reptiles and 30 mammals species. Although, sadly, there are many species which either no longer occur, or simply occur in very small numbers among the islands, eg. Caiman latirostris (caiman), Chrysocyon brachyurus (maned wolf), Eunectes notaeus (yellow anaconda), Lutrinae sp. (otters), Panthera onca (jaguar), Puma concolor (puma) and Tayassuidae sp. (peccaries). [3, 22, 23, 24]
In La Azotea – La Jaula small tributary many fish species were found. Some of them are endemic, other ones are migratory species that frequent waters near the Paraná river. Below it’s possible to find a list of all fish species that were found in the biotope under review: Abramites hypselonotus, Acestrorhynchus pantaneiro, Ageneiosus inermis, A. militaris, Apareiodon affinis, Aphyocharax anisitsi, A. dentatus, Apistogramma borellii, A. commbrae, Apteronotus albifrons, Astyanax asuncionensis, A. correntinus, A. erythtropterus, A. rutilus, A. stenohalinus, Australoheros facetus, Brycon orbygnianus, Bryconamericus exodon, B. iheringii, Callichthys callichthys, Catathyridium jenynsii, Characidium zebra, Charax stenopterus, Cheirodon interruptus, Cichlasoma dimerus, Cnestrodon decemmaculatus, C. raddai, Corydoras hastatus, C. paleatus, Crenicichla lepidota, Cynopotamus argentus, C. kincaidi, Cyphocharax platanus, C. spilotus, C. saladensis, Eigenmannia trilineata, Farlowella hahni, Galeocharax humeralis, Gymnogeophagus balzanii, G. cf. setequedas, G. meridionalis, Hemisorubim platyrhynchos, Hisonotus maculipinnis, Homodiaetus anisitsi, Hoplias malabaricus Hoplosternum littorale, Hyphessobrycon anisitsi, H. eques, H. luetkenii, H. meridionalis, Hypoptopoma inexspectatum, Hypostomus boulengeri, H. cochliodon, H. commersoni, H. latifrons, H. ternetzi, Imparfinis mishky, Leporinus obtusidens, L. striatus, Lepthoplosternum pectorale, Loricaria luciae, Loricariichtys platymetopon, Luciopimelodus pati, Metynnis mola, Moenkhausia dichroura, Mylossoma duriventre, Odontesthes perugiae, Odontostilbe paraguayensis, O. pequira, Oligosarcus jenynsii, Otocinclus arnoldi, O. vestitus, Oxydoras kneri, Phalloceros caudimaculatus, Pimelodella gracilis, Pimelodus albicans, P. maculatus, Potamorrhina squamoralevis, Potamotrygon brachyura, P.motoro, Prionobrama paraguayensis, Prochilodus lineatus, Psectrogaster curviventris, Psellogrammus kennedyi, Pseudobunocephalus iheringii, Pseudopimelodus mangurus, Pseudoplatystoma corruscans, P. reticulatum, Pseudotylosurus angusticeps, Pterobunocephalus depressus, Pterodoras granulosus, Pterygoplichthys anisitsi, Pygocentrus nattereri, Pyrrhulina australis, Rhamdia quelen, Rhamphichthys hahni, Rhaphiodon vulpinus, Rhinodoras dorbignyi, Rineloricaria lanceolata, R. parva, Roeboides affinis, R. descalvadensis, R. microlepis, Salminus brasiliensis, Schizodon borellii, Serrapinnus calliurus, S. kriegi, Serrasalmus maculatus, S. marginatus, Sorubim lima, Steindachnerina brevipinna, Sternopygus macrurus, Sturisoma robustum, Synbranchus marmoratus, Tetragonopterus argenteus, Thoracocharax stellatus, Trachelyopterus lucenai and Triportheus nematurus. [1, 20, 21, 23, 24, 25]
It’s still possible to find some amphibians, crustaceans and reptiles in this zone too, like: Chaunus arenarum, C. fernandezae, C. scheneideri, Elachistocleis bicolor, Leptodactylus chaquensis, Odontophrynus americanus, Palaemon argentinus, Phrynops hilarii, Physalaemus albonotatus, Scinax nasicus and S. squalirostris. 
List of plants found in the nature biotope: The flora in La Azotea – La Jaula is mostly composed by plants of the genera Panicum, Paspalum, Echinochloa, Eleocharis and Polygonum. These plants are intertwined with each other, and form a network of roots, stems and leaves of about 2 to 5 m, from the coast of the tributary, occupying the entire column of water. This fact promotes an excellent refuge for fish. In addition, this network creates a passive retention system of free aquatic plants – so it is possible to find the presence of plants from de genera Eichhornia, Pontederia, Pistia and Limnobium there. However, once again, it is important to keep in mind, that in different periods of the year, the water level changes and it can easily modify what was described. In addition, the literature review allows us to conclude that it is possible to find all the following plant species in this area: Cyperus entrerrianus, Echinochloa crusgalli, Echinodorus grandiflorus, E. uruguayensis, E. macrophyllum, Eichhornia crassipes, E. azurea, Eleocharis sp., Gymnocoronis spilanthoides, Hydrocotyle sp., Juncus sp., Lemna minor, L. gibba, Limnobium laevigatum, Ludwigia elegans, Myriophyllum aquaticum, Nymphoides indica, Panicum sabulorum, Paspalum inaequivalve, Pistia stratiotes, Polygonum punctatum, Pontederia cordata, Sagittaria montevidensis and Salvinia sp.. [9, 12, 15, 23, 24, 25, 26]
Threats to the ecology: Even if the tributary La Azotea – La Jaula is inserted in a National Park, where riverside forests appear with exotic tree species as dominant, all this natural area is surrounded by zones that present an intense landscape modification, due to an excessive agricultural and livestock activities, that origin a low environmental quality. Plus, the industrial activity developed in areas close to the water courses, and the proximity to urban centers, generates a negative impact, mainly due to the spill of waste and sewages, which affect water quality and the diversity of this region wetlands, because they constitute a source of eutrophication and degradation of the environment, as it should not be forgotten that the biotope area is flooded, seasonally, every year.
Lastly, it is necessary to control the problems associated with the invasion of exotic trees like Fraxinus sp., Gleditsia tiracantos, Ligustrum lucidum, and Morus alba. [9, 15, 19, 26]
Sources of information: This project was only possible because of the precious help of Drª. Adriana Almirón, from Universidad Nacional de La Plata, Argentina, and the biologist Pablo Giorgis that gave me precious informations about this biotope.
 ALMIRÓN, Adriana; CASCIOTTA Jorge; CIOTEK, Liliana; GIORGIS, Pablo. Guía de los Peces del Parque Nacional Pre-Delta. 2nd ed. Argentina: Editorial APN, 2015.
 FERNANDEZ, Marcelo. Biodiversity of the rio Paraná Delta, Argentina. C. E. Fish Essentials (blog), 2015.
 ACEÑOLAZA, Pablo G.et al. Biodiversidad del Parque Nacional Pre-Delta. INSUGEO, Miscelánea 12: 169-184, Tucumán, 2004.
 08-visitando parque pre-delta, diamante, entre ríos, https://www.youtube.com/watch?
 Pequeño tramo del arroyo “La Azotea”: Para caminantes de senderos,
 A 300 metros del Parque PreDelta en Diamante –https://www.youtube.com/
 MIRANDE, Virginia et al.; Características fisicoquímicas y bacteriológicas de los ambientes acuáticos del PNPD posteriores a un período de aguas altas; Fundación Miguel Lillo; LILLOA 47; 1-2; 106-116, 2010.
 MIRANDE, Virginia et al.; Evaluación abiótica y biótica de ambientes acuáticos de un parque nacional entrerriano; Fundación Miguel Lillo; LILLOA; 49; 2; 127-134, 2012.
 KHARDINA, Natasha – Biotope Aquarium Project responsable, e-mails exchanged on 08/07/2019.
 MALVÁREZ, Ana Inés; Las comunidades vegetales del Delta del Río Panrana. Su relación com factores ambientales y patrones del paisaje. PhD thesis. Faculdad de Ciencias Exactas y Naturales. Universidad de Buenos Aires. 1997.
 BLEHER, Heiko. Bleher’s Biotopes.1st ed. Pavia: Aquapress Bleher, 2014.
 BENZAQUÉN, Laura et al.; Sistemas de paisajes de humedales del Corredor Fluvial Paraná-Paraguay, 1st ed. Buenos Aires: Secretaría de Ambiente y Desarrollo Sustentable de la Nación, 2013.
 ROSSO, Juan José; Peces Pampeanos guía y ecología. 1st ed. Buenos Aires: L.O.L.A., 2007.
 SCHUBERT, Franz. Plants and animals of Argentina-Nationalpark Pre Delta at Rio Parana. Trekkingchile (blog) 2018.
 https://sib.gob.ar/area/APN*PD – viewed on 04/10/2019.
 MENNI, R. C.. Peces y Ambientes en la Argentina continental. 1st ed. Buenos Aires: Museo Argentino de Ciencias Naturales, 2004.
 RODRIGUEZ, Estela Elizabeth; ACEÑOLAZA, Pablo; MUÑOZ, Juan de Dios. Catalogo de la flora vascular del PN Pre Delta. Misiones: SIB, 2007.