Cory Fry Deaths

[Cinnebuns]

Today, while cleaning my fry tank, I found 6 dead panda cory fry. Deaths happen in breeding but 6, especially with the small scale doing, is a lot and makes me take notice. I did some much better cleaning today because of it and did it twice. Both times I filled 2 gallons in a bucket from my turkey baster. I don't even wanna know how many times that took lol. 

It surprised me how much dirtier the tank was today compared to every other day but i also noticed something that could possibly be the issue. To prevent more deaths I would like to figure out if this is it. This is actually largely why I sucked out so much water because the particles in question are large and fall out of a turkey baster easily. 

They are large particles that almost look like salt crystals. I doubt it actually is salt or it would dissolve into the water. I suspect it's left over substrate from the previous owner. When i got the tank it still had a small amount of substrate in it. I cleaned it out multiple times before using it, but any substrate likes to stick around for decades. The guy said it was a planted substrate with sand. To me, neither of those sound dangerous to a cory but idk. 

Parameters check out at ammonia: 0, nitrite:  0, nitrate: 10 before the cleaning and water change. 

Any input if that's the possible issue? Any ideas of what else it might be?

[Fish Folk]

How large is your fry tank?

Is it a bare bottom?

How is it filtered?

What are you feeding and how often?

Fry sometimes die from (1) foul water (2) improper feeding (3) predators (4) inability to breathe (5) getting stuck

[Cinnebuns]

On 5/9/2022 at 7:04 AM, Fish Folk said:

How large is your fry tank?

10 gallon seperated. 1 was found dead on one side and 5 on the other. I suspect the side that the 5 were found the ramshorn snails also aren't doing so well as they have become more pale but I can't say for sure. The snails on the other side are doing very well and I even saw a new collection of eggs. 

On 5/9/2022 at 7:04 AM, Fish Folk said:

Is it a bare bottom?

Yes. 

On 5/9/2022 at 7:04 AM, Fish Folk said:

How is it filtered?

2 nano ACO sponge filters, one on each side. Until recently one side (the side that had more deaths) had a small instead of a nano. 

On 5/9/2022 at 7:04 AM, Fish Folk said:

What are you feeding and how often?

Used to be first bites. They are also housed with guppy fry who all seem to be doing well so their feeding often is associated with how the guppies are fed.  I do put newly hatched cory fry in with the youngest possible guppy fry so they tend to correlate similar in age. 

Now that both sides are older (6 weeks and 2.5 months) I have been feeding bug bites and occasionally throw in a mini algae wafer.  I usually feed 3-5 times a day in small amounts. I'm starting to consider cutting that back to 2-3 for these since they are now older but keep 3-5 for the younger ones in a different tank. 

On 5/9/2022 at 7:04 AM, Fish Folk said:

Fry sometimes die from (1) foul water (2) improper feeding (3) predators (4) inability to breathe (5) getting stuck

I did notice that 2 that were alive on the bad side were looking pretty pale so there's something going on. I just started with the bug bites instead of first bites a couple of weeks ago so I wonder if that's a factor. Could foul the water more. I thought maybe it was causing them to not get enough but it does drop down pretty quickly.