Sterbai corydoras too small

[beastie]

So, I have a mixed aged group of sterbai corydoras. Both groups bought as juveniles, I had something wipe out half of my population after obtaining the second group, so instead of having 20 as planned, I ended up with 13.

Anyways, half or so would be about a year, half would be two years old and they are just so darn small. I assume like 3,5cm max? They are smaller than my smallest b-ram which I obtained in february, and in adulthood both should be the same size. I guess it is feeding, so I will need some advice on there. Here are some pictures next to the b-rams or amano shrimp

 

So to the feeding, I feed once a day, with two days not feeding at all in the week. I feed mostly frozen, bbs, cyclops, daphnia, always mixed with something larger, mosqito larvae, artemia, bloodworms (once a week), tubiflex (once a month). I feed some sort of algae wafers for otocinclus/amanos around lights out time, spirulina, chlorea, repashy super green, blanched vegetables, any of this every third or fourth day.

Some of the days I will feed live - bbs, microworms, mosquitos in the summer (I pour them in so they reach the bottom) some of the days I will feed dry food, hikari vibra bites, fluval bug bites, dennerle shrimp king, sera vipan, cichlid gold pellets. This tank has the most fish, I feed a lot so I hoped the corydoras would get something to eat. They are not scared of the other fish, as you can see they will swim under a b-ram, no issue. The ember tetras and rummynose tetra are so fat, I do not think I am feeding too little. 

 

How come they are not growing? Is this normal growth rate?

[jwcarlson]

I've had six sterbai for going on two years.  They're spawning, so I think it's safe to say they're mature.  That said, I think the biggest one is 2" or so.  The trouble is, I've got no idea their history.  I bought them smallish from the LFS, but who knows how old they are when you buy them and what their care was like leading up to that.  I've never really heavily target fed them until recently, but mostly relied on just feeding a lot.  I don't think I starved them, but probably could have done a better job feeding them when they were younger.  

Mine are at least fattening up now, I'm feeding them two freeze dried tubifex worm cubes daily.  As well as a lot of the other stuff you feed, but not all of that either.

I stick the tubifex to a small pebble and sink them and the corys go nuts for them.  I have no idea if mine are the right size or not, I think sterbai are supposed to get up to 2.5"?  So I'm not sure they'll be as big as your ram.  But I've never kept rams.  As far as why yours aren't growing like you think they should... have you wormed them?  It looks a bit like maybe their bellies are a bit sunken in, but it could just be the pictures.  Does that seem accurate to you when you view them in person?

[Odd Duck]

Sterbais are slightly smaller on average compared to many cory species, 2”-2.6” (total length) I think is the general expected. Mine are almost all about 2” with a couple females a bit bigger.

@beastie Are you measuring total length (nose to end of tail) or standard length (nose to tail base)?

[anewbie]

I have around 20 sterbai; the males do stay fairly small - around 2 inches but the females can get massive - quite wide and approach 3+ inches. I two that are just monsters that all the little males constantly follow around. My newer ones are only a year old but the old ones are 5+ years. I had a bunch scattered across different aquariums and when i moved i collected them all and put them in the 450 together.

[nabokovfan87]

On 11/13/2023 at 8:35 AM, beastie said:

So, I have a mixed aged group of sterbai corydoras. Both groups bought as juveniles, I had something wipe out half of my population after obtaining the second group, so instead of having 20 as planned, I ended up with 13.

Can you show some photos of the group?  Smaller could very likely just be a male, but I do have a similar thing in my tank where there are what seem to be "runts."  I would think of them as corydoras that are last to get the meal or just slightly more timid than others.  Having more cover might make them comfortable, but you could just as easy spread found around and try to target feed the smaller ones. Everything you're doing seems to be right, the fish looks fine, but if you're concerned just increase feeding.  Feed 6 days a week with every other day having a night meal.  (doesn't have to be heavy, but that gives the more timid ones a chance to feed while others sleep)

[beastie]

On 11/13/2023 at 11:05 PM, Odd Duck said:

Are you measuring total length (nose to end of tail) or standard length (nose to tail base)?

Erm, I took a tape measure, put it in front of the glass, waited until fish swam by in the correct position and squinted at it to guesstimate. How are you supposed to do that, if you cant catch them and do it physically

[beastie]

They dont want to hang out in front of my camera, so I fed tubiflex and took pictures of some groups.

None of the sterbais is significantly larger. I hope I do not have all males, what a coincindence that would be 🙂

 

[Andy's Fish Den]

From what I can tell from the pictures, they look good, I would not worry. As long as you see them scooting around the tank and nose down checking out the substrate, they are good. It sounds like you feed them enough. the only thing I would suggest if you aren't doing it already, put some sinking food in the tank after the lights go out for the night. that way, the upper level swimming fish are not in feed mode and the food will sink down to the bottom and the sterbai will be hunting and find it. 

The smaller ones most likely are males, I have a group of sterbai in my discus tank that spawn for me regularly, and a few of the males are quite a bit smaller than the females, and they were all bought around the same time and size.  

[Odd Duck]

On 11/14/2023 at 3:51 AM, beastie said:

Erm, I took a tape measure, put it in front of the glass, waited until fish swam by in the correct position and squinted at it to guesstimate. How are you supposed to do that, if you cant catch them and do it physically

I don’t mean that you have to physically measure them, just asking if you’re estimating standard length (to tail base) or total length (to end of tail).  There would be at least 1/2” difference between those measurements in sterbais, more in larger species of cories or longer finned species or varieties.  It’s like the difference in length between a betta’s body vs his length including his tail.  Or a veil tailed angelfish.  Many fish are measured by body size, not total length.  Cories are generally reported in total length since they don’t typically have exuberant finnage like a long finned pleco, for instance.

 

Edited November 14, 2023 by Odd Duck
Clean up typos.

[nabokovfan87]

On 11/14/2023 at 3:14 AM, Andy's Fish Den said:

From what I can tell from the pictures, they look good, I would not worry.

Agreed. They all look healthy and normal to me.  I'll snap some pictures of mine to give you an idea of the variation I'm seeing.

For measuring, this might help.  It's what Odd Duck is speaking about.

Edited November 15, 2023 by nabokovfan87

[Lennie]

This is the size of a female sterbai compared to female rummynose bleheri from this morning. There is no male in the tank all females currently so the females were getting even thicker during breeding mode sometimes

rummynose even standing closer to the glass

Ladies from their old tank, about a year old or so

[jwcarlson]

Here's mine and the *new* way that I'm feeding them tubifex.  For some reason my sinking pebble method has started failing and the worms slip off very early instead of holding on and mostly staying where the fish can get them.  I had a worm cone that doesn't work at all (in my opinion), so I cut the end off and hot glued a 1/2" stainless washer inside the bottom of the cone, it fits two good sized tubifex cubes pretty well.  It seems to be working really well and almost no wasted worms.  Also, some pictures of my breeding group for reference.  I've had these about two years.

 

 

Edited November 21, 2023 by jwcarlson

[Mary W.]

Maybe you have a variant or subspecies that is just naturally smaller?  They look healthy and happy from your pictures -

[nabokovfan87]

I had intended to follow up and show the size discrepancy I'm seeing in my own tank.  I have 4 adults, the rest were all born on the same spawn.

The rightmost fish here is an adult.



I apologize for the angle of the photo and the fuzziness through the glass.



Here I am trying to show the full scope and size differentiation.  Yes, some of this is simply male vs. female fish, but there's also slower growing "runts" in the group.

[beastie]

@nabokovfan87 they are georgeous though 🙂 I will just feed more after lights out with the sinking, which cant always be the live/frozen, cause of the tetras

Will see, I dont have breeding hopes anyways now. The tank is too crowded at this moment