Dry and Rainy Seasons in the Tank
by Kristian Adolfsson
of Sweden
General:
Many fish from tropical areas spawn seasonally due to changes in their natural environment. Most often they spawn when the rainy season begins, because it brings increased food supply and increased possibilities for the fry to find food and shelter. Re-creating as many of the changes as possible that occur during the rainy season's beginning might be one way to spawn species that otherwise are very difficult to spawn. Many species are so easy to spawn you need not use the often cumbersome methods that are described below, but certain species and groups of species might need them. First try the general rules for breeding a certain species or group of species, but if you don't succeed, try the suggestions below.
The following is a compilation of a way to breed fishes that come from areas with marked dry and rainy seasons, e.g. the Amazon and Rio Negro areas of South America. Data and ideas have been collected from a lot of different sources; including books, friends and the Internet, and are based on my own experiences 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 eaters, which are thought to be very difficult to spawn.
Spawning triggers in nature:
Below follows a list of the different changes that can occur during the rainy season's beginning and that might trigger a species to spawn. They are not listed in any particular order, and which of them various species need to spawn is not fully known.
- Low pressure
After a long period of high pressure at the end of the dry season, the barometric pressure falls in connection with the first rain.
- Increased food supply
After a starvation period during the end of the dry season the food supply increases drastically. Certain species look like skeletons at 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.
- 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 onto 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.
- Increased water flow
The rain results in increased flow of water. The fish become more active. Some species migrate upstream to get to calmer and more suitable spawning areas.
- Increased oxygen levels
Rain that falls on the water surface increases the oxygen level in the water. 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.
- Dilution of dissolved substances in the water
The longer the dry season lasts, the more salts, humic substances and organic material are concentrated in the water that remains. When the rain starts the concentration of these substances decreases due to dilution. The river, the stream etc. is diluted with rainwater that has zero hardness, which lowers the hardness and often even the pH.
- Change in water temperature
Water temperature is often lowered due to cloudiness and the cold rainwater. In high terrain temperature differences are often greater than down in the lowlands (10ºC compared to a few degrees).
- Change in water depth
Increased water volume causes the water to deepen. Water pressure at the bottom increases and the fish get a larger vertical swimming space. Distance to the water surface will be longer for species that go to the surface to catch air.
- Spawning sites become available
At the end of the rainy season there is often water only 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 newly flooded areas with plants, roots, tree trunks and shadows, in which to hide eggs and give the fry a better chance to hide.
- 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 in the morning before it gets light and it darkens faster in the evening.
Even light angles vary from one part of the year to the other. The further 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).
- Increased plant plankton level
When the rainy season occurs this increases in certain waters. This is also a signal to the adult fish to spawn because there is food for smaller fry.
- Right time of the year
Certain species have a very strong "biological clock" that is linked to when the rain and dry seasons occur in their natural distribution area.
- Other fish spawn
Hormones in the water from other fish spawns might prompt another species to spawn.
- 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?
Below are suggestions on how to simulate the different stimuli that are listed above. Which to choose depends on which species is to be bred. Certain species might require only a few, e.g. good feeding and a water change with lower water temperature, while others need most of the items from the list. The list below follows the same order as above:
- Low pressure
Many have written about their fish having spawned during periods of low pressure. However, the same species might in many cases have spawned during a period of high pressure if the right circumstances had been present. 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 the passage of a period of low pressure. A barometer might be good to have handy to check the trend for air pressure.
- Increased food supply
If fish are in good condition when they are set to spawn, they can manage to starve for several weeks. When feeding begins again, this will trigger the instinct to spawn.
- Changed food types
A change of food might trigger a spawn. In some waters in South America the amount of mosquito larvae increases (especially white mosquito larvae) at the beginning of the rainy season. If you don't feed mosquito larvae before setting a species to spawn, and then begin to feed with them during the simulated beginning of the rainy season - this will simulate the change.
- 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 - e.g. in front of the filter outflow.
- Increased oxygen levels
Use an 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 diffuser can also be used.
- Dilution of dissolved substances in the water
Build a higher level of humic substances ( e.g. peat and alder cones) and salts (fertiliser, CaCO3, MgSO4) during the simulated dry season. Later, dilute with as soft water as possible when the rainy season begins (preferably RO water).
- Change of 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 just 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.
- Change in water depth
Lower the water level to 25% of normal during the dry season. Increase it to normal level over a couple of days when the rainy season begins.
- Spawning sites become available
Change the plants and decorations. If gravel is not used, plant plants in pots and move caves and roots to make a new environment more suitable for spawning.
- Changes in the light
- Light intensity: With several bulbs on the tank, it's easy to turn off all but one (or perhaps use only daylight). Another way 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 further from the equator the larger difference between the seasons. Shorten by 1-2 hours in both morning and evening. Use a timer!
- Light angle: Hard to simulate in the tank.
- Increased plant plankton level
Not possible to simulate easily in the tank, but one might try infusoria. Even if this does not stimulate spawning it might be a good first food for certain species with very small fry.
- Right time of the year
Wild caught fish might require that it should be rainy season time in the area from where they come, for them to spawn in our tanks. Check exactly where the species comes from and when the rainy season occurs there. Captive bred fish have generally 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 at a different time than when they normally spawn in nature.
- Other fish spawning
Let an easily bred species spawn in the same tank as the more difficult one. This works as a natural hormone treatment. An alternative might be to let an easily spawned species spawn in a separate tank, and add water from it to the difficult species' tank.
- 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. This does make the water harder, but it might be the change in water chemistry that makes certain species spawn.
- Move the well-fed fish from a 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 occur might get the fish to spawn (good way to breed many tetras).
Suggestions for a breeding scheme:
Preparations and tips:
Choose a tank of the right size for the species in question. The tank should have a volume that will be enough when only 25% of the aquarium is filled with water. The most important issue is that the oxygen level is kept high enough without filter and air stones. Arrange for hiding places and a few plants. The tank should simulate the end of the dry season.
- Bottom substrate
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 of bottom material:
- Some species prefer a dark bottom, others 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 (e.g. Corydoras).
- Eggs that fall to the bottom are harder for the parents to find and eat.
- No reflections from the bottom.
Disadvantages of 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. These can be easily disinfected and be cleaned of snails etc.
- The tank should be filled with water from the tank where the fish were before, and have the same temperature. Make sure the water has been recently changed (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, 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 too low pH levels when you add the peat etc.
- Choose healthy and mature animals with the right ratio of males to 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 for 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.
Beginning of the dry season:
Food supply decreases and ceases. Water level and current decreases. Temperature of the remaining water increases.
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 by 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's 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 rainfall:
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's temperature should be about 3 degrees lower than that of the tank. Put in the filter and run it at half speed if possible. One could try to turn off the light for a couple of hours in the middle of the day to simulate thick clouds. Lower the heater temperature by 2 degrees. Feed a little with mosquito larvae and newly hatched brine shrimp. Add infusoria so that the water gets a slight cloudiness.
Day 22. Add the equivalent of 20% of the tank volume, with water about 5 degrees lower in temperature than the tank. Run the filter at full speed and make it "splash" in the surface. Lower the heater temperature by 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 for your product.
Day 23. Add the equivalent of 20% of the tank volume. The water temperature should be about 5 degrees lower than that of the tank. Add aeration at a low level. Lower the heater temperature by 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 temperature should be about 5 degrees lower than that of 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.
Height of the rainy season:
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!
