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Emerald dwarf rasbora breeding


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Hi all!

I have a little group (originally 7, now 9) of emerald dwarf rasbora in my 10 gallon. I have had them all since July 2022. They started spawning and producing some fry around September 2023, which was around the time I started feeding a bit more variety and volume (higher protein flake/pellet foods, frozen worms, and frozen brine shrimp). I would see 3-4 fry at a time through the fall, and 2 survived up to this point. When I was seeing fry, I would crush hikari micro pellets into a powder and provision at water surface (where babies hung out) 2 times a day. I also made sure I kept a lot of floating plants to try and provide a refuge for the fry. Otherwise doing nothing to help with fry survival.

Note that I'm not really trying to breed them, I just like having some babies survive here and there. 

Over the past month or so, I have noticed no new fry in the tank at all. I don't have many females (2 of 7 sent to me were female) so I know that could be an issue. 

The main change during this time is the temperature of the tank has gone from around 74 F avg to 69-70 F avg, as this is an unheated tank. 

Does this species tend to not produce as well/at all in lower temps? 

Thank you for reading!

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Hi @cmo1922. Just in my own personal experience as an unheated tank keeper and accidental breeder- temperature definitely plays a part.  Breeding temps typically range higher than lower though weirdly sometimes cool water changes also trigger activity. I see more breeding activity in my tanks in the hotter months because my tanks are warmer even in my temperature regulated home. However in the cold months they probably run from 70-74 and in the summer from 72-78. Many people when purposefully breed recommend water changes and feeding higher protein foods. This is part of the fun- if you're not breeding on purpose just take notes of your water conditions/food temps and see what pans out! 

And yes your fish are fine in your cooler waters I'd say into the mid to high 60s does them no harm- you just may get no breeding activity. 

Edited by xXInkedPhoenixX
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Thank you @xXInkedPhoenixX! Good info to keep in mind! I was confused because I learned that this species likes a little cooler water than other tropical fish, so I wasn't sure their breeding would be affected if they were still "within acceptable range" for the species.

My paleatus cories breed like crazy when the temps drop...I love discovering all these differences as I try new species in my tanks!

Here is a pic of the wild tank where the rasboras live - as you can see it would be impossible to try and collect eggs in here with all that grass, to see if I could improve survival rates! I've never been able to spot one egg in there...


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If you are an aquarium coop member, I just listened to a great talk about egg scatterers by Randy Carey which he gave a year ago explaining how they breed and how to do replicate it as well. A high protein, fat and heavy diet will help condition the fish and higher temperatures definitely play a role in spawning. Usually egg scatterers only spawn during certain times of the year and you have to replicate those conditions to trigger them to spawn. Usually it happens during the rainy seasons which involve more abundant food, higher temperatures followed by a quick temperature decrease due to rain.  

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