How to simulate rainy season in a blackwater biotope aquarium?

[Blackwater guru]

This is my 145 liter blackwater biotope aquarium that I set up during early january this year almost 5 months ago although the aquarium itself was purchased during late december 2019.

I also forgot to mention this is my first aquarium so far and I really love how natural and beautiful everything looks.

I currently have around 30 fishes in there with 15 of them being my wild caught cardinal tetras and 8 of them are corydoras duplicareus catfish.

In terms of filtration I use an undergravel filter manufactured by my local fish store and it has been working wonderfully thanks to maintenance such as water changes and gravel vacuuming being done once a week.

My goal with this tank is to simulate the living conditions of these fish which usually are rainforest blackwater rivers in south america and to do that I use roiboi tea bags that I put in my aquarium along with some dried botannicals such as dried oak leaves or dried seed pods.

Now what I am really interested in at the moment is to breed some of the fish that I have at the moment especially the tetras and to do that I need to create more optimal breeding conditions.

From what I have read cardinal tetras and especially wild caught specimens will breed once the rainy season starts which is something I would have to simulate in order to succeed.

If I ever breed my cardinal tetras how would I simulate the rainy season in a home aquarium?

 

[PheonixKingZ]

Very cool tank!

You could maybe get a spray bar to simulate rain.

@Byron should be able to help you with biotope stuff. That’s his department.

 

[Retired Viking]

One thing I have done is not turn on the tank lights to simulate the rainy/cloudy season and just have a little light from the windows. I had red eye and glow light tetra have fry but my neon and ember did not. Make sure your water is very soft. I plan on trying again after the lock down when I can get more RO water. I also do a major water change,

 

[Byron]

Each water change is a rainstorm to the fish. You don't need to have a six-month "rainstorm" because the fish will respond to the environmental aspects of the beginning of the rainy/wet season and once is all it takes. If it fails, repeat a week or two later. As you've mentioned Paracheirodon axelrodi (cardinal tetra), this fish has what Baensch termed a light phobia, so darkening the tank may be helpful.

Do a substantial water change, with the temperature just a tad cooler. Some will suggest a tad warmer, but I do not know if there is actual evidence this is better or just someone's idea. A change in pH is sometimes also suggested, the thinking being that a massive influx of water (rain) that is sufficient to flood the surrounding forest up to 30 feet in depth is going to raise the pH a bit, but this too has questions. Rain is likely to be on the acidic side, since water is a powerful solvent and readily assimilates substances it comes into contact with, such as CO2 in the air. Also, the incredibly thick layer of organic matter is going to lower the pH in no time, as there is no buffering (GH and KH are zero).

Another proven trick is to do this water change on a day of low pressure; fish can detect atmospheric pressure, and they know that a low pressure system means storm and rain.

 

[seangee]

That's going to be tough. They recognise changes in the weather by changes in barometric pressure. @Byron can explain this better than I but you can't trick them into thinking its going to rain unless it actually is going to rain.

When the pressure does drop significantly you can re-inforce the idea by doing a large water change using water that is 2-3 degrees cooler than the normal tank temp.

You should note that cardinal eggs and fry are extremely light sensitive. Add that to the corys in your tank yor chances of actually breeding them in the main tank are close to zero, but you could use a breeding tank that is kept dark.

 

[Colin_T]

The easiest way to simulate the wet season to encourage Corydoras to breed, is to do a 75% water change each day using water that is a couple of degrees cooler than the tank water. You can gravel clean the tank at the same time.
Make sure any new water is free of chlorine/ chloramine before it's added to the tank.

If you want to breed cardinal tetras, you need water with a GH of 0 and a pH below 7.0.
Feed the fish 3-5 times a day for a couple of weeks before breeding them.
Separate males and females for 4 or 5 days and then put 1 male and 1 female together in a tank with a bit of Java Moss. Leave them together for 24 hours or until the female has shed her eggs (she will look skinny). Then move the adults out of the breeding tank and cover the tank in black card to prevent light getting in. Wait for the eggs to hatch then start feeding the babies.

Get food for the babies ready before you breed the adults. The following link has information about culturing live foods for baby fish.

Back to Basics when Breeding Fish

STARTING OUT Make sure you have a pair, (1 male + 1 female). There is nothing worse than spending your hard-earned dollars buying a couple of fish to try and breed and ending up with a pair of fish of the same sex. Let's face it, to reproduce fish you need a male and a female. Two males won't do...

www.fishforums.net

 

[Blackwater guru]

That's going to be tough. They recognise changes in the weather by changes in barometric pressure. @Byron can explain this better than I but you can't trick them into thinking its going to rain unless it actually is going to rain.

When the pressure does drop significantly you can re-inforce the idea by doing a large water change using water that is 2-3 degrees cooler than the normal tank temp.

You should note that cardinal eggs and fry are extremely light sensitive. Add that to the corys in your tank yor chances of actually breeding them in the main tank are close to zero, but you could use a breeding tank that is kept dark.

Eventually once my economy allows it I will purchase a breeding tank along with an undergravel filter and possibly a sponge filter to go with it.

To darken it I could cover it with dark towels or even newspaper but using floating plants such as salvinia or amazon frogbit would also be a great idea.