Julii Cory fry help

[Adamsh]

Hi All,

I have been trying to raise cory fry for about 8 months now. 2 adults in the tank seem to be laying roughly 8 eggs every 9 to 14 days, Out of all of those eggs only 2 have ever made it to adulthood and are happily swimming now in the adult tank.

I have a fry tank (25 litre Fluval edge), which newly layed eggs are transplanted to, none of the eggs fungus over and all hatch. However slowly and surely every fry die over the course of a week.

I used to vacuum the bottom of the tank every couple of days, but have since stopped, and to be honest since stopping, the fry in the tank have lived longer than most (about 2 weeks so far), although I did find 2 dead ones today.

What am I doing wrong to have such a poor survival rate? was I over cleaning the sand? I haven't touched it for 2 weeks now, and although I can see a build up of waste on the sand the fry seem to be doing better, water parameters are good (0 ammonia, 0 nitrite) and I partial water change every 14 days using water from the adult tank.

I used to feed the JBL nova Powder food, this is what I successfully raised 2 fry into adult hood with, but have had 0 success since. I am now feeding frozen baby brine shrimp which I can see they are eating as their little bellys are pink.

Thanks in advance

[bekateen]

Hi @Adamsh,

I wonder if your problem isn't water quality and insufficient aeration. I get a lot of trilineatus eggs (which might also be what you actually have), and I lose a lot of fry as they age.

Cheers, Eric

[Adamsh]

I wonder if you can be too caring when it comes to trying to raise these fry.

I thought it might be my black sand, so I syphoned it all out and replaced it with a finer white sand. I left the black sand in the bucket with about 3 inches of water as I was sure a couple of eggs got sucked in.

Fast forward to today, I check the bucket which has had no water flow, food or aireation and sitting in the bottom looking up at me was one of the biggest fry I have seen for a long time. While his brothers and sisters who were fed twice a day and had water changes in a dedicated planted tank died one by one.

I currently have 3 fry alive and 14 eggs (new batch), I've stopped with the water changes and vacuumed the sand once in 9 days and they seem to be doing better than the last lot.

As an experiment I've dropped 2 eggs into a small tank of water with some plants and moss (no water movement and no aireation) I want to see if they do better than the eggs in the fry tank.

[Adamsh]

Fry tank

Experiment tank

[bekateen]

I've had that same experience before with a few different fish species and with aquatic frogs. Usually there are a few common factors involved here:

1. How much water (depth-wise) was in the bucket? Even if you have no aeration or circulation, a shallow bucket of water will remain well oxygenated if the water has a high surface area-to-volume ratio.
2. You aren't adding food to the bucket. In typical fry tanks, I know I tend to overfeed the babies, to ensure they all have food and to encourage fast healthy growth. But excess food means uneaten food, which will pollute the water unless you do water changes often (which although necessary can also be stressful). And
3. only one or two fry survive in the bucket - with so few fry in the bucket, you don't need much food and the fry can survive on the small number of infusoria in the water and the limited amount of (probably low quality) food particles that were transferred into the bucket when first filled. These few fry also won't produce much urinary and fecal waste, when compared to how much made by 20 or 50 or 100 fry. So again, water changes aren't as critical.

In other words, yes, this strategy can work (but is not guaranteed to work) with one or two babies for some species. But it is not capable of working with an entire clutch of a lot of eggs.

Cheers, Eric

Edit: You posted photos while I was typing my post: Now I see the water level in the bucket is relatively shallow, which is good. Plus the plants will produce some oygen (especially in strong sunlight which they appear to have), and this bucket would probably grow lots of infusoria.

P.S., Nice tanks... And cute Pirate Kitty!