[Zoidburg]

1.) Get a GH/KH liquid test kit

2.) If they are voracious eaters, then feed 15-30 minutes prior to turning on the lights. Make sure to feed near the glass so you can see the shrimp best. Once they have congregated near the front, turn on the lights to see if you have any females

3.) If they aren't voracious eaters, then don't feed the colony for at least a few days. Then try doing as instructed in #2

 

[Jamo33]

@Zoidburg
If you remember my initial start with my colony of blue neos did something very similar.
Grain of salt with this, completely anecdotal.
I had a load of berried females and they kept on dying, to the point I went from 8 to 1 from my initial 20 shrimp. Deaths were noticeable as I had few numbers, but especially present in females and particularly berried females. Turns out I was fighting my buffering soil with gh/kh remineraliser rather than just gh.
My guess as to why this happened.
All shrimp experienced the same water parameters and changes but males could freely shed/molt. Females however, died each time they tried to molt. So, if you are having any issues like I was then maybe look at the water changes and behaviours etc.

Of course this could all be entirely pointless and useless, but its possible you are having similar problems.

Hope you do find out mate.

 

[Zoidburg]

@Jamo33 Yeah, I recall. SplitSix doesn't have a buffering soil, plus tank is 3 years old, which is past what most buffering soils will last, especially with KH! (unless the soil was replaced at any time during the setup... but I don't see anything to indicate this is an issue?)


As per SplitSix, KH is about 10, GH is over 10. Without those liquid test results, we wont know for sure!


I'm thinking though that there's got to be some females in there! I feel like I can see a few in the photos, too... however, if we can examine them when they are the lightest (right when the lights come on), this may help to know for sure.

 

[Quint]

Do males also get the stripe down there back? Thought I read only females do. Saw at least one in the pic with a stripe.

 

[SplitSix]

Ok, going to keep this tight. We've got direction provided by Mr. Zoidburg:

1.) Get a GH/KH liquid test kit
If they aren't voracious eaters, then don't feed the colony for at least a few days.

I am getting a GH/KH kit today. I might be a few days on delivery if I go online but I will provide some more reliable Hardness numbers. My current testing method is year old API 5-in-1 strips.

I'm not going to feed the tank for 3 days. The tank has a high degree of bio-film, algal growth, and plant biomass:

I will report back with better numbers and a more adequate population sample. Let's draw everyone out for a banquet.

Do males also get the stripe down there back? Thought I read only females do. Saw at least one in the pic with a stripe.

I do not see one but I know what you're talking about. I read up on that about a year ago. I balked at understanding the information. It would have to be the accumulation or depletion of some type of matter on or directly under the carapace, right? And, it only applies to females? I need to understand that happening. I may have long witnessed a symptomatic indicator of an absence or abundance in the environment that I didn't correct.

But, I like the optimism shown by @Zoidburg. I think it's the correct move. Nothing is conclusive or substantiated. I'm anxious based off of a midday single observation. Time to validate observation - We're gonna do a slight fast and then ring a dinner bell to better ascertain whether or not the females were hiding. My wife and I did feed the tank about 2 to 3 hours into the plant photo period. I didn't think the behavioral differences between the sexes would vary that much or be that apparent. Here's to hoping.

I'll update after I've gotten better data to present. And, thank you so very much for your input, experiences, and direction. I came here in need and you're providing direction based on expertise. I'll do my best to respect your efforts by providing timely, quantifiable information.

Thank you again for the responses,
Split

 

[Zoidburg]

The racing stripe generally is a female trait, but lack of one doesn't indicate male. Here's one older thread with a link to a picture of a female with one.

https://www.plantedtank.net/forums/...ates/1292435-neocaridina-changing-colour.html


SplitSix, great tank! Lots of cover! With all those plants, I imagine it would be hard to pick out any good sized females. I imagine that many may not have just grown to full size yet.

 

[Blue Ridge Reef]

I'm thinking though that there's got to be some females in there! I feel like I can see a few in the photos, too....

I concur. In photo #2 the shrimp to the farthest right (the one with her tail tip behind the stalk) is almost certainly a female. But I see more males than makes any sense. I can count 17 that I'd bet money are males, and only one that I'd wager on being a girl. Very odd. Hoping the ladies come out of the woodwork when you feed after their fast! Please keep us updated.

 

[Quint]

I have noticed that in my tank many/most of the larger females stay near the plants or up on the intake sponge and such. Not in all cases but usually the berried females stay near the dense cover areas. When I feed most of the ones coming out front will be males, juveniles, and 2 or 3 females. The males are more apt to swim all over the tank in the open as well especially when I am trying to do water changes.

As far as the racing stripe in my tank it happens on probably 1/3 of the females. More so in the wild types but a couple of RCS and when I had them black emeralds (chocolates) also got it. Have not scene a single male with the stripe.

Good luck and goon on following Zoidburgs advice. Another way to look around is come down at night with a dim flashlight and take a look around. Alot of things come out of the woodwork at night.

 

[Zoidburg]

Taking a closer look at one of the pictures, I think I even see a berried female in the far back!

 

[Bio]

Edit: I just noticed your temps. At your temperature, there are likely to be more males born than females. At 26c, the temp of your tank, there has been observed 1/5 female to male ratio of new born shrimp. Since your tank has 3 years of breeding, that could be the original factor creating the current shift in population. The study I read this in:

Serezli, Ramazan & Atalar, Sina & Hamzaçebi, Sevim & Kurtoğlu, İlker Zeki & Yandi, Ilhan. (2017). To what extent does temperature affect sex ratio in red cherry shrimp, neocaridina davidi? The scenario global warming to offspring sex ratio. Fresenius Environmental Bulletin. 26.

Unfortunately, combining the above and below factors, your situation does not seem that unexpected. At 20 C (68f), the m/f born is reversed, and a 23 C (73.4), it is 50/50.

If my hypotheses are correct, then I suggest culling out some males over time to maintain a higher shrimp breeding population.​

I hope you got this situation sorted out, or got some information on what is going on.

I don't know from personal experience, but I have heard that when males start to out number the females, it can have a cascading effect. Other more experienced shrimp keepers please feel free to correct any falsehoods that I might be propagating.

The decline in females may be because, when males outnumber the females, it puts a lot of stress on the females. With inordinate numbers of males trying to mate with fewer females, it can cause harm and injury to the females. As the female population decreases, this has a snowball effect, and the problem gets worse over time.

With that in mind, something else may have caused the decline, and this phenomenon may have exacerbated the situation.

Some more information in a video by Shrimp Life

 

[Blue Ridge Reef]

Wondering if there's a temperature at which the female ratio wouldn't be quite high if low enough? When I used to breed leopard geckos, you could determine the gender of eggs 100% by what temperature they were incubated. It would be pretty sweet if OP's gender numbers could be reversed simply by unplugging the heater for 6 months.

 

[Bio]

Wondering if there's a temperature at which the female ratio wouldn't be quite high if low enough? When I used to breed leopard geckos, you could determine the gender of eggs 100% by what temperature they were incubated. It would be pretty sweet if OP's gender numbers could be reversed simply by unplugging the heater for 6 months.

Yeah somewhere between 20 C (68f) and a 23 C (73.4f). However, with the situation how it currently is, more direct intervention might need to be employed. Also the other tank inhabitants might not take so kindly to the temperature change, if there are any?

 

[Blue Ridge Reef]

Interesting. 20c/68F is roughly where most of my tanks stay all of the time and I seem to get a pretty even ratio. They seem to carry eggs a lot longer than in my heated tank is the only difference I've noticed. At 77F I'd wager that they go from saddled to berried to babies inside of 3 weeks. I've got cool tanks with females that have been berried about that long. An aside, I wouldn't know this if it weren't for starting tank journals and seeing dates and photos of individual shrimp so I'm a big advocate of taking lots of photos and starting a journal. Besides the fact that I want to see everyone else's set ups and shrimp!

And yeah, agree 100% that culling some males would be prudent. In a tank with a normal ratio the males can go absolutely nuts when a female molts. I can only imagine such a scenario in OP's aquarium.

 

[Bio]

Interesting. 20c/68F is roughly where most of my tanks stay all of the time and I seem to get a pretty even ratio. They seem to carry eggs a lot longer than in my heated tank is the only difference I've noticed. At 77F I'd wager that they go from saddled to berried to babies inside of 3 weeks. I've got cool tanks with females that have been berried about that long. An aside, I wouldn't know this if it weren't for starting tank journals and seeing dates and photos of individual shrimp so I'm a big advocate of taking lots of photos and starting a journal. Besides the fact that I want to see everyone else's set ups and shrimp!

And yeah, agree 100% that culling some males would be prudent. In a tank with a normal ratio the males can go absolutely nuts when a female molts. I can only imagine such a scenario in OP's aquarium.

Yes eggs develop quicker at higher temperatures, compared to lower. Not all set ups are going to see the same results under the same temps as well. And that is just one study I linked, I've not seen any replications yet. It's just s small sample.

I'm a big fan of keeping a journal too, it is how I like to do things.

 

[madcrafted]

Interesting. 20c/68F is roughly where most of my tanks stay all of the time and I seem to get a pretty even ratio. They seem to carry eggs a lot longer than in my heated tank is the only difference I've noticed.

I've noticed the same thing in my breeding tanks. I have had some lines (caridina) breed as low as 64° and the females typically carried between 42-45 days. No noticeable change in sex ratio when compared to summer breeding where temps are closer to 73°. I seem to get close to an even ratio of males and females, regardless. Controlled captive breeding for decades could play a part in that. Our food sources don't exactly run low in our tanks like they do in natural streams during seasonal changes.

 

[Bio]

I've noticed the same thing in my breeding tanks. I have had some lines (caridina) breed as low as 64° and the females typically carried between 42-45 days. No noticeable change in sex ratio when compared to summer breeding where temps are closer to 73°. I seem to get close to an even ratio of males and females, regardless. Controlled captive breeding for decades could play a part in that. Our food sources don't exactly run low in our tanks like they do in natural streams during seasonal changes.

In I gave the wrong impression, the research mentioned only applies the cherry shrimp.