Too many fish! What to do about overstocking?

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moxysnork

Aquarium Advice Newbie
Joined
Jan 29, 2021
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I bought 20 dwarf livebearers (Heterandria formosa/ least killifish) in 2019. They reproduce a LOT and now I have an infinite number in my 20 gal tank - at least 60. They are dying. There are too many of them, and I can't keep the water quality at a healthy level.

So, what do I do?
A) Sell the fish online or to a local fish store so they can sell them to their customers as pets
B) Sell them/ give them away as feeder fish

The problem with Selling them is that nobody is familiar with the species, so they don't want them, and they might die soon anyway.
I don't actually know if they are suitable to use as feeder fish for other species.
Is there an option C?

~~~~


For reference, here are the answers to the basic "unhealthy fish" questions.

I have a single-species tank of Dwarf livebearers aka Least Killifish (a misleading name - they are not a type of killifish) aka Heterandria formosa. There are also pond snails and a few plants in the tank.

1~ The fish are dying. At this point at least one per day.
2~ NO2 level is 0, NO3 level is about 40-60. (yes, that's way too high.) pH is 7.5.
3~ The tank is 20 gal. I set it up in June 2019 with the plants first. The pond snails came with the plants. I added 20 Heterandria formosa fishes in August 2019.
4~ The filter is an Aqueon Quietflow 20.
5~ These livebearers are very prolific, and I don't know how many there are. My guess is 60+, a mix of juveniles and adults. Adults are about an inch long.
6~ I do water changes and gravel vacuums about once/week, about 20% each time.
7~ I've had the fish since August 2019
8~ The issue has been worsening over time. I have recently started using an anti-algal, and also an ammonia reducer, but this was not what started the problem.
9~ I have been feeding them Tetracolor Tropical Flakes all along. I did try giving them frozen brine shrimp gumdrops a long time ago but they are too big for the fish to eat
 
Too Much Fish

I don't know what it's like in your neck of the woods, but here the fish store owners are very nice about accepting the results of one's overpopulation. I've walked in unannounced (didn't call first) and asked if I could give them what I could no longer manage. Every time they graciously gave the little buggers a new home. They say it happens: people move away, or the tank population gets out of hand, etc, so it's a common thing. Beyond that, I like the idea of helping a local store by giving them something from which they can make a bit of profit.
 
I'm not familiar with the species, but what's the tank's temperate? Do you heat it? If you use a heater, would reducing the temp slow reproduction?

Wish I could be actually helpful, but maybe this bump will get someone with more knowledge to see it.
 
I bought 20 dwarf livebearers (Heterandria formosa/ least killifish) in 2019. They reproduce a LOT and now I have an infinite number in my 20 gal tank - at least 60. They are dying. There are too many of them, and I can't keep the water quality at a healthy level.



So, what do I do?

A) Sell the fish online or to a local fish store so they can sell them to their customers as pets

B) Sell them/ give them away as feeder fish



The problem with Selling them is that nobody is familiar with the species, so they don't want them, and they might die soon anyway.

I don't actually know if they are suitable to use as feeder fish for other species.

Is there an option C?



~~~~





For reference, here are the answers to the basic "unhealthy fish" questions.



I have a single-species tank of Dwarf livebearers aka Least Killifish (a misleading name - they are not a type of killifish) aka Heterandria formosa. There are also pond snails and a few plants in the tank.



1~ The fish are dying. At this point at least one per day.

2~ NO2 level is 0, NO3 level is about 40-60. (yes, that's way too high.) pH is 7.5.

3~ The tank is 20 gal. I set it up in June 2019 with the plants first. The pond snails came with the plants. I added 20 Heterandria formosa fishes in August 2019.

4~ The filter is an Aqueon Quietflow 20.

5~ These livebearers are very prolific, and I don't know how many there are. My guess is 60+, a mix of juveniles and adults. Adults are about an inch long.

6~ I do water changes and gravel vacuums about once/week, about 20% each time.

7~ I've had the fish since August 2019

8~ The issue has been worsening over time. I have recently started using an anti-algal, and also an ammonia reducer, but this was not what started the problem.

9~ I have been feeding them Tetracolor Tropical Flakes all along. I did try giving them frozen brine shrimp gumdrops a long time ago but they are too big for the fish to eat


Do you think you have enough oxygen to support that amount of fish?
 
I second taking them to a LFS. I would say you need to act immediately if you are having deaths and severe water quality issues. I would be honest with the LFS and let them know your situation. And at this point, I wouldn't even worry about selling them- I would be giving them away for free to anybody who will take good care of them.
 
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