7 replies to this topic

[EastFish]

I have a 20 gallon Blackwater setup for a couple of weeks with Heterandria Formosa and Pygmy Killifish but there are already dozens of live-bearer fry and it's only been a few weeks. Any suggestions for a small predator to keep the population under control but be peaceful towards the adults. Would Pygmy sunfish eat the fry? I'm going to move the adult females to my Scarlet Badis tank for the time being, hoping that they will eat any remaining fry that they're still holding. However the conditions in the native tank aren't suitable for the Badis. I also want the population to reproduce just not this quickly.

Edited by EastFish, 11 August 2020 - 09:07 PM.

[swampfish]

I struggled for a couple of decades to get Heterandria formosa to reproduce enough to survive more than two or three years in my aquaria. I have finally found that they like soft, low pH water, my rainwater, with live food. However, those are the same conditions that I have found that pygmy killifish require to thrive. So if you want fewer Heterandria, you probably need separate tanks.

 

Others have good luck feeding flake food to Heterandria, so the secret to my previous poor luck was likely my tap water that I used to keep them in. It is well water with a pH of 6.8 but a hardness (GH) that is too high to be read with an aquarium test kit, the KH is almost off the high end of the scale. I assume that water hardness may reduce reproduction as the caught Heterandria lived long lives but had only a few babies of both sexes. They grew to adulthood, but there were apparently too few in the next generation to maintain the population. 

 

Previous pygmy killies I have had died after a few months in my well water. Three years ago, I started putting them in rainwater in a bog pond outdoors and keeping them indoors during the winter in rainwater with newly hatched brine shrimp and now have more than I can give away.

 

Phil Nixon

Illinois

[JasonL]

Might consider tossing in a couple darters eg. swamp darters.  They are very predatory towards fry in my experience.

[Joshaeus]

I struggled for a couple of decades to get Heterandria formosa to reproduce enough to survive more than two or three years in my aquaria. I have finally found that they like soft, low pH water, my rainwater, with live food. However, those are the same conditions that I have found that pygmy killifish require to thrive. So if you want fewer Heterandria, you probably need separate tanks.

 

Others have good luck feeding flake food to Heterandria, so the secret to my previous poor luck was likely my tap water that I used to keep them in. It is well water with a pH of 6.8 but a hardness (GH) that is too high to be read with an aquarium test kit, the KH is almost off the high end of the scale. I assume that water hardness may reduce reproduction as the caught Heterandria lived long lives but had only a few babies of both sexes. They grew to adulthood, but there were apparently too few in the next generation to maintain the population. 

 

Previous pygmy killies I have had died after a few months in my well water. Three years ago, I started putting them in rainwater in a bog pond outdoors and keeping them indoors during the winter in rainwater with newly hatched brine shrimp and now have more than I can give away.

 

Phil Nixon

Illinois

A common poecillid that DOESN'T like hard water?! Weird! Oh well...I'll keep that in mind if I keep them some day. From what I've read, softwater fishes are considerably more sensitive to KH and TDS than GH or PH (sudden changes in KH being the most common killers in 'PH crashes').

 

I'm curious...why would keeping pygmy killies with the hets prevent the OP from effectively controlling the latter's population?

[swampfish]

Joshaeus: What is the OP?

[Joshaeus]

Joshaeus: What is the OP?

Oops! That's the original poster. 

[swampfish]

My pygmy killifish tend to just "hang" in the aquarium among the plants rather than be active swimmers. They don't even seem to get excited when they are fed, although they will move leisurely to the area of the tank where I introduce newly-hatched brine shrimp. The Heterandria formosa are considerably more active, but they also spend a lot of time just "hanging" out. I suppose this behavior in both fishes is a method of blending with the plants and reducing predation from larger fish.

 

With that behavior, I suspect that it would be easy for Heterandria fry to avoid capture by the adult pygmy killies. On the other hand, the pygmy killie fry would be small enough to be consumed even by older Heterandria fry.

 

In the Tate's Hell area of Florida, I have found mixed populations of pygmy killies and Heterandria, but it is more common to find them in separate marshes or in different areas of the same marsh. They may be less compatible than one would think.

 

Phil Nixon

[EastFish]

The pygmy's weren't there for population control they just seemed like compatible fish. I'm talking about adding another fish. The conditions obviously suit the Heterandria because the population is exploding which is great, I just don't want to have to kill them, although I suppose I could feed them to other fish. I haven't seen any killi fry FYI.