Dry and Rainy seasons in the Aquarium.

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Author: Kristian Adolfsson, MAF, ka@roka.se

The following is a compilation of a way to breed fish that come from areas with marked dry and rainy seasons i.e. the Amazon and Rio Negro areas in South America. Data and ideas have been collected from a lot of different sources, both from books, friends and the Internet, and are based on my own experience of breeding catfishes and tetras from South America.

This simulated dry and rainy season cycle takes about 4 weeks to go through. Using a simpler method people have been able to breed Panaque nigrolineatus, Sturisoma sp., and Siamese algae eater, which are thought to be very difficult to spawn.

Spawning triggers in nature

 
1. Low pressure
    After a long period of high pressure in the end of the dry season the  barometric pressure falls in connection with the first rain.  
2. Increased food supply
    After a starvation period during the end of the dry season the food supply  increases drastically. Certain species look like skeletons during the end of  the dry season and have perhaps been without food for more than a month.  Certain species even eat detritus to get some nutrition.  
3. Changed food types
    During the dry season the scarce food might consist of bottom dwelling  animals (red mosquito larvae) and decaying plant parts. When the rainy  season starts the food changes to insects that fall down on the surface,  mosquito larvae (especially white and perhaps black) and other water  insects, pollen from flowers, seeds, fruits, fresh leaves and eggs and fry  from other species that have begun to spawn earlier.  
4. Increased water flow
    The rain results in increased flow of water. The fish have to get more  active. Some species migrate up-stream to get to calmer and more suitable  spawning areas.  
5. Increased oxygen levels
    The rain that falls on the water surface increases the oxygen level in the  water. The increased water flow also makes the oxygen level increase. In  many cases a high oxygen level is a condition for the eggs and fry to make  it during their first days.  
6. Dilution of dissolved substances in the water
    The longer the dry season lasts, the more salts, humic substances and  organic material will be concentrated in the amount of water that remains.  When the rain starts the concentration of the above mentioned substances  decrease in the water due to dilution. The river, the stream etc. is diluted  with rainwater that has zero in hardness, which lowers the hardness and  often even the pH.  
7. Change of the water temperature
    The water temperature is most often lowered due to cloudiness and the cold  rainwater. How big the difference is, depends on from where the fish comes.  In high terrain the temperature differences are most often larger than down  in the lowlands (10?C compared to a few degrees).  
8. Change in water depth
    The increased water volume causes the water surface to rise. The water  pressure at the bottom increases and the fish gets a larger swimming space  vertically. The distance to the water surface will be longer for the species  that goes to the surface to catch air.  
9. Spawning sites become available
    At the end of the rainy season there is often only water in the middle of  the river or stream and there are very few plants or hiding places. With  increasing water depth, the fish can find new flooded areas with plants,  roots, tree trunks and shadows to be able to hide eggs and give the fry a  better chance to hide.  
10. Changes in the light
     The amount of light and duration of light decreases due to  cloudiness in connection with the rain. Certain parts of the day can be very  dark during the most intense rain. With more clouds in the sky it takes  longer time in the morning before it gets light and it darkens faster in the  evening.
     Even the angle that the light penetrates the surface varies from one  part of the year to the other. The longer from the equator, the more the  variation.
     Note that certain species want almost complete darkness to spawn (they live  under dense vegetation, among tree roots and in black water).  
11. Increased plant plankton level
     When the rainy season occurs the amount increases in certain waters. This is  also a signal to the adult fish to spawn because there is food for smaller  fry.  
12. Right time of the year
     Certain species have a very strong "biological clock" that is  linked to when the rain and dry seasons occurs in their natural distribution  area.  
13. Other fish spawn
     Hormones in the water from other fish that spawns might affect another  species to spawn.  
14. Sound
     Even the rain's splashing against the surface might be a signal to spawn.  Maybe also the sound of thunder.

How do we simulate these things in the tank?

 
1. Low pressure
    Many have written about their fish having spawned during low pressures. The  same species might in many cases spawn during a high pressure if the right  circumstances are present though. Low pressure is of course impossible to  simulate in a tank, so keep an eye on the weather forecasts and start a  simulated rainy season during a passage of a low pressure. A barometer might  be good to have handy to check the trend for the air pressure.  
2. Increased food supply
    If the fish are in good condition when they are set to spawn they can manage  to starve for several weeks. When the feeding later begins again this will  trigger the instinct to spawn.  
3. Changed food types
    A change of composition of food might trigger a spawn. In some waters in  South America the amount of mosquito larvae increases (especially white  mosquito larvae) during the beginning of the rainy season. If you don't feed  mosquito larvae during the time before setting a species to spawn and then  begin to feed with them during the simulated beginning of the rainy season  is a way to simulate the change.  
4. Increased water flow
    Easily solved with different forms of pumps and filters. Certain species lay  their eggs close to the largest water flow in the tank, in front of the  outflow of the filter.  
5. Increased oxygen levels
    Use air driven filter and air stones. One can also let a motor filter  "splash" in the surface to increase the amount of oxygen. An air  diffusor can also be used.  
6. Dilution of dissolved substances in the water
    Build a higher level of humic substances (i.e. peat and alder cones) and  salts (fertilizer, CaCO₃, MgSO₄) during the simulated  dry season. Later dilute with as soft water as possible when the rainy  season begins (preferably RO water).  
7. Change of the water temperature
    Use submersible heaters to keep the temperature up during the dry season.  Note that certain species can't take too high or too low temperatures and  that certain species prefer high temperatures to spawn. These species  perhaps seek out flooded grassy areas to spawn where the sun heats up the  shallow waters.
    To lower the temperature one only decreases the setting on the submersible  heater until it can be turned off. To further lower the temperature one  might ventilate the room or put an ?ice block? in the tank.  
8. Change in water depth
    Lower the water level to 25% of normal during the dry season. Increase it to  normal level during a couple of days when the rainy season begins.  
9. Spawning sites become available
    Change the plants and decorations. If no gravel is used, plant plants in  pots and move caves and roots to make it a new environment more suitable for  spawning.  
10. Changes in the light
     Light intensity: With several bulbs on the tank, it's easy to turn  off all but one (or perhaps only use daylight). Other ways might be to put  paper between the hood and the cover glass.
     Light duration: At the equator the duration of light is about 12-14  hours year round. The longer from the equator you get the larger the  difference between the seasons. Shorten with 1-2 hours each in the morning  and evening. Use a timer!
     Light angle: Hard to simulate in the tank.  
11. Increased plant plankton level
     Not possible to simulate easily in the tank but one might try with infusoria.  Even if it does not stimulate the spawning it might be a good first food for  certain species with very small fry.  
12. Right time of the year
     Wild caught fish might require that it should be during the rainy season in  the area from where they come, for them to spawn in our tanks. Check exactly  from where the species comes from and when the rainy season occurs there.  Captive bred fish have most often had their sense of when it is the rainy  season and when it is not reduced and might often be bred year round. The  same could be true for young fish that are wild caught. If they have not  experienced a rainy season it might be easier to breed them during another  point of time than when they normally spawn in the nature.  
13. Other fish spawning
     Let an easily bred species spawn in the same tank as the more difficult one.  It works as a natural hormone treatment. An alternative might be to let an  easily spawned species spawn in a separate tank, and take water for the tank  with the more difficult species from the tank where the easily species  spawns.  
14. Sound
     Add water through a plexi glass plate with lots of very small holes. The  drops that fall through simulate the rain beating on the water surface.

Further ideas that are used by breeders are:

 
• Filter over limestone during the simulated rainy season. Does make the  water harder but it might be that the change in water chemistry that makes  certain species spawn.  
• Move the well-fed fish from one tank without optimum conditions (no  spawning substrate, "wrong" water parameters, many fish that are  "disturbing", etc.) to a tank with the right conditions for  spawning. The move itself together with all the changes that occurs might  get the fish to spawn (good way to breed many tetras).

Suggestion of a breeding scheme

Preparations and tips

 
• Bottom material  

  Whether to use bottom material or not can be debated. The most common is  to have some kind of gravel but peat or filter floss can be used. When a  bottom material is used it will help increase the surface for good bacteria  to multiply.

   

  Advantages with bottom material:

   
   
  • some species prefer a dark bottom, other a pale one. Some pale  Corydoras prefer a pale bottom.  
  • many species "like" to probe around in the bottom for food  
  • less risk of fungus attack on bottom dwelling fry (i.e. Corydoras)  
  • eggs that fall to the bottom are harder for the parents to find and  eat  
  • no reflections from the bottom
   
   

  Disadvantages with bottom material:

   
   
  • Difficult to see if all food has been eaten  
  • Difficult to clean without vacuuming out sand/peat
   
   

   

   
•  

  If you don't know how the fish spawn you have to set up the tank with a  little of everything. The plants can be varied with large leafed plants  (Java fern, Echinodorus, Anubias, and Hydrocotyle), fine leafed (Myriophyllum,  Cabomba, and Egeria), narrow leafed (Vallisneria) and other (java moss,  Najas). Large plants can be planted in pots for easy removal. Use roots,  plastic pipes of different diameters, etc. Plastic plants can be used  instead of live ones. The can be easily disinfected and be cleaned from  snails etc.

   
• The tank should be filled with the water from the tank where the fish were  before and have the same temperature. Make sure the water has been changed  newly (low nitrite and nitrate levels).  
• A filter with adjustable flow should be used.  
• The light hood should be able to give a high light level.  
• The heater should be mounted along the bottom but yet be easy to adjust.  Make sure it's a good quality heater that can be fully submerged.  
• Cover the sides and top with paper to avoid scaring the fish when you are  moving about in the room.  
• Do not feed white or black mosquito larvae before the spawning attempt.  
• Make sure you have peat (black peat is preferable), alder cones, leaves,  peat extract or whatever you want to use. Make sure that the carbonate  hardness is at about 2-3 kH to avoid to low pH levels when you add the peat  etc.  
• Choose healthy and mature animals in the right proportion between males  and females depending on the species and put them in the breeding tank. They  should be well fed to be able to survive a two-week dry season period.

Simulation scheme

End of rainy season. 

Still some food and the water level has not started to lower.

 

Day 1. Feed about 1/10 of normal. The lights should now have a level  between full power and "cloudy", about 14 hours. Filter running at  full speed.

 

Day 2. Lower the water level about 10%, feed 1/10 of normal. Add  some calcium carbonate and magnesium sulphate to raise total and carbonate  hardness 1 degree each. (An alternative is to take out 20% of the water and  add half the amount with hard tap water if that's available.) Add a dose of  plant fertiliser according to instructions of your product (gives more  dissolved salts in the water).

 

Day 3. Lower the water level about 10%, skip feeding. Increase the  temperature about one degree.

 

Day 4. Lower the water level about 10%. Increase total and carbonate  hardness 1 degree each. Feed 1/10 of normal. Put peat, alder comes, leaves,  etc. in the water. Tannins etc. will be leached from these items over the  coming days.

The beginning of the dry season. 

Food supply decreases and ceases. The water level and current decreases. The temperature increases in the remaining water.

 

Day 5. Lower the water level about 10%, skip feeding. Increase the  temperature about one degree. Decrease the flow by adjusting the filter. Check  pH.

 

Day 6. Lower the water level about 10%, feed 1/10 of normal.

 

Day 7. Lower the water level about 10%. Increase total and carbonate  hardness 1 degree each. Stop feeding until day 21. Increase the temperature  about one degree.

 

Day 8. Lower the water level about 10%.

 

Day 9. Lower the water level about 10%. Increase total and carbonate  hardness with 1 degree each. Shut off air stones. Take out the filter and  clean it. Let the filter run in another tank so it has a working bacterial  culture when it's needed in a week.

 

Day 10. Lower the water level about 10%. The water level should be  down to 25% of the tank capacity. The temperature should be around 28 degrees.  Put peat, alder comes, leaves, etc. in the water. Add plant fertiliser.  Increase the lighting to max. Take away any floating plants. Start an  infusoria culture. Check pH.

 

Day 11-19. Leave the fish in peace.

Beginning of rainy season. 

The first clouds can be seen in the sky but no rain has started to fall.

 

Day 20. Clean the filter that has been working in another tank.  Decrease the lighting, both the intensity and the length (down to about 10  hours). Take out the peat, leaves etc. Check the pH.

First rain fall.

 

Day 21. Put the floating plants back in. Add more plants of the type  the fish like for spawning. Add clean, as soft as possible, water (preferable  RO), about 20% of the tank volume. The water should have about 3 degrees lower  temperature than the tank. Put in the filter and run it at half speed if  possible. One could try to turn off the light a couple of hours in the middle  of the day to simulate thick clouds. Lower the temp on the heater 2 degrees.  Feed a little twice with mosquito larvae and newly hatched brine shrimps. Add  infusoria so that the water gets a slight cloudiness.

 

Day 22. Add the equivalent of 20% of the tank volume. The water  should be about 5 degrees lower in temperature than the tank. Run the filter  at full speed and make it "splash" in the surface. Lower the temp on  the heater 2 degrees. Feed a lot and often. Add infusoria so that the water  gets a slight cloudiness. Add a vitamin product and plant fertiliser according  to instructions of your product.

 

Day 23. Add the equivalent of 20% of the tank volume. The water  should be about 5 degrees lower in temperature than the tank. Add aeration at  a low level. Lower the temp on the heater 2 degrees. Feed a lot. Add infusoria  so that the water gets a slight cloudiness.

 

Day 24. Turn off the heater if the fish can take such low  temperatures. Aeration at half speed. Fill the tank. The water should be about  5 degrees lower in temperature than the tank. If you can, open a window during  the night to lower the temp further. Feed a lot. Add infusoria so that the  water gets a slight cloudiness.

 

Day 25. Aeration at full speed. Change 50% of the water volume. Feed  a lot.

 

Day 26-?. Carry on as day 25 until they spawn!