Corydoras julii(?) dying upon introduction

[ArchimedesTheDog]

1. Water parameters
a) Temperature: 78.6 Fahrenheit
b) 6.4 pH
c) 14 dGH
d) 4 dKH
e) TDS - no idea, tap is supposedly around 300 but not sure what the substrate buffering does to it
f) 0 Ammonia, 0 Nitrite, 10 Nitrate
g) Weekly 50% water change
h) Using Prime for water change treatments. Was dosing Excel but laid off it for the moment after losing fish. Weekly I add a half dose of a comprehensive macro/micro fertilizer for plants getting nutrients out of the water column

2. Tank set up
a) Size - 20 gallon High
b) Substrate - Fluval Plant and Shrimp Stratum
c) Filtration - Aquaclear 50 HOB filter
d) Furnishings - some Malaysian driftwood, moss, Cryptocorynes, Java Fern, Staurogyne Repens
e) Other tank mates - Betta, Cherry Red Shrimp
f) How long has it been set-up? - about a month, fully cycled, biofilter was consuming 3ppm ammonia per day before fish were introduced.
g) Food used and frequency - Hikari sinking wafers every other day
h) Recent changes in the tank - Not applicable, only change ion the tank was the addition of the cories

3. Symptoms / Problem description or history - I picked up five Corydoras julii from my local fish store on Monday. The fish are housed in a large tank system with many species in divided subsections. The LFS had had this batch for nearly three weeks. A few of them looked a little placid, shall we say, but I didn’t worry about it at the time.

I brought them home and drip acclimated them for an hour in a small breeder box, then added them to the tank. All five seemed to be happy and healthy and wriggling their way around the tank. I shut the lights off and went to work.

Eight hours later I returned home to find three of them very sluggish, mostly sitting still on the floor of the tank. Overnight, these three died. A further one died the next day while I was at work. But the last is going gangbusters, just happy as a pig in mud.

A few days later I added two more from the same batch to see what would happen, sam one hour drip. These two were highly active in the tank at the store. Sure enough, one of these died overnight, but the other stayed alive, so now I have two living in the tank. The one from this later pair that lived seems to be stressed at times, surfing the glass a lot. Easy to tell the difference from the original survivor due to smaller size and narrower body shape (I suspect one male and one female).

Not sure what to do to improve the chances of further fish living, could use some advice. 2/7 seems like pretty poor survival rate. I'd obviously like to get the school up to happier numbers for the fish. Only suspicion is that I should have waited for a mor mature tank? Not sure what that would have done pragmatically though.

Just for sanity’s sake, here’s a photo, are they actually trilineatus?



4. Action taken (if any) - Stopped Excel but not sure that was the culprit

5. Medications used (if any) / changes in fish observed since treatment began (if any) - none

[bekateen]

Hi ArchimedesTheDog,

First, welcome to PlanetCatfish.

Sorry about your losses. That's rough; I think most of us have had an experience like this at one time or another.

Just looking at the photo you provided, the fish shown (which by the way is

Corydoras trilineatus

, not

Corydoras julii

; a common misidentification at virtually every fish store in the USA) looks rather skinny and unhealthy to begin with. Did all the "julii" corys look like this at the pet store? What pet store did you purchase them from? An independent LFS or a chain store?

You say the tank is one month old, fully cycled. Do you mean the cycling took place in this month, or was it fully cycled and then operating for a month? How long have you had the betta and shimp in the tank. Did they come from the same LFS? Have any other fish died in the tank?

If it's not a cycling issue, you might ask the LFS to check their water params for you, to see how their water compares to yours. Maybe the two waters are very different.

Regards, Eric

[ArchimedesTheDog]

Thanks. I appreciate the identification, I was hoping I had gotten true Julii but wasn't certain. I went out of my way a few years ago to get true julii in another tank but couldn't recall the way to identify them. I got the livestock all from the same source, an independent LFS here in San Diego. Other livestock in the tank seem healthy and were added at the same time so the Betta didn;t have time to get territorial about the tank. It's hard to tell health with the shrimp as they hide a lot and I never see more than 1-3 at a time: the ones I see are robust.

All of their "jullii" (trilineatus) did look like this, I thought they looked a bit small but I figured they were juveniles and would fill in, and if they lived for three weeks in the store they would be healthy enough. Would a longer than one hour acclimation help? I will investigate their water parameters.

My tank was set up for a month, and was cycled for about a week before introduction of livestock, water testing every day to ensure the stability of the biofilter. Ammonia was consumed all the way through to Nitrates reliably with 0ppm Ammonia and Nitrites throughout the day, every day.

I may return the living ones as they are not the species I wanted and instead add Sterbai to the tank, another species I considered.

[Bas Pels]

Looking at the numbers, I think the water is a bit warm, 73 F would be better than 78 F, but that cannot be the reason why the fish died.

What is so odd is, the fish either die soon, or they survive. That is, I don't think the problem is in your water, or in your tank, but either in getting used to this - or the fish in the store are less then perfect. Not having visited this shop, I won't go deeper in this line of thought.

What I would do is getting a group, say another 5, from another store, and ideally I would want to know their water parameters.

Even if this helps, it could still be the getting used to your tank, the fish in the store could very well be OK - and still die on you.