Cory Fry Dying

[ChemEng]

Tank size: 20L
pH: 7.4
ammonia: 0
nitrite: 0
nitrate: ~20
tank temp: 22-24 C

Fish Symptoms (include full description including lesion, color, location, fish behavior): They appear pale and lethargic. The already dead fish look like there is something wrong with their faces particularly their eyes - almost like a growth (I don't have a magnifying glass so its hard to tell if it is a fungal growth).
I first noticed there was something wrong this morning after yesterdays water change, since they were all very lethargic and weren't eating. Before the water change I caught the babies and placed them into a breeding trap so that I could clean the tank more thoroughly. I have been feeding them on a mix live and decapsulated brine shrimp since 2 days after they first hatched. Since yesterday I've done another 50% water change and added water ager, half the recommended dose of tonic salt and also the recommended dosage of Aqua-Septic made by AristoPet, since I suspected it might a bacteria infection since I couldn't see any physical clues to anything else at that stage.

Volume and Frequency of water changes: Weekly Changes of 50%

Chemical Additives or Media in your tank: Sponge and carbon filter. Water ager added with water changes.

Tank inhabitants: Approx 40 2.5 week old peppered corydoras fry

Recent additions to your tank (living or decoration): Previous heater cracked, so the only new addition is a brand new heater

Exposure to chemicals: haven't used any fly sprays or anything that I can think of around the tank (It's in my bedroom)

Substrate: Sand

Tank has been up and running for 3 weeks with a previously cycled filter added.

One last note: I live in Christchurch, New Zealand and they still recommend that we boil our drinking water since the February 22nd earthquake, maybe there was something in the water when i did my water change. Although the fish in my main tank seem fine since their water change.

 

[weezawoo]

Can I ask how often and what you are feeding? My first batch of cory fry went very wrong. I was using liquifry and put too much in, it makes the water toxic if too much is added. On the other hand, when I went away for a weekend and left my BFs mum instructions to feed all my fish she forgot the babies and they died from not enough food. After lying there dead for a while they then seemed to grow a furry type growth on them but that was only after they died. It could just be a feeding issue especially with that many in a small tank.

 

[ChemEng]

I've been feeding them at least 2-3 times a day maybe more if I'm up late at night or early in the morning. I feel at times I could be over feeding them but usually all the brine that I put in gets eaten within 5minutes.

This morning most but not all of the babies didn't have their usual pink bellies full of brine, even though they have only gone their usual 8-10 hours over night without being feed. It's possible that some on the brine has become stuck under the sand and started to decay without me even seeing, although if this was the case wouldn't I see a spike in my ammonia and nitrite levels?

 

[This Old Spouse]

Why are you adding salt to your water?? Corys do NOT like salt.

 

[ChemEng]

I umm'd and arr'd about using the salt with the babies but from the research I've done on salt being good/bad for corys is about 50/50 so this is why I only did half the recommended dose. I've used it at half dose in my main tank a few times before and it hasn't affected my adult corys at all.
The reason I added the salt in the first place is that I've read from a few places that salt helps to kill off any bad bacteria in the tank since I hadn't remembered at that stage the other treatment that I had hidden away in my box of fish stuff.


Just a note to others than might comment: I won't be able to reply to more posts for a 7 hours since it's time for bed but I'll answer all I can in the morning before uni.

 

[weezawoo]

I never used salt with mine so I haven't had experience so cant comment on that. But how deep a layer of sand is there? I found with fry it is much better so have very little or no sand at all. I have just a tiny sprinkling, so little that you could still see the bottom of the tank a bit. It is nicer than bare but too much I think you do risk bits getting trapped which is more deadly to the little ones! I only fed mine once in morn and once in evening.

 

[ChemEng]

My layer is sand it about 1-1.5cm thick. Just deep enough so that I can plant some plants in there so they have some cover. I've been making a well in the sand so that I can feed the decapsulated brine in there, that way if there is left over brine that they don't eat I can easily remove it before the next feeding. I'll try feeding them less often since if anything I would currently be over feeding them

 

[ChemEng]

The remaining fry died over night. I'm going to give the tank a complete clean and begin cycling it again and hope that the corys will lay eggs again soon.

This time I'll remove all the sand and just place a thin layer on the bottom like you said. I think what you said about the feedings might be right so I'll cut them down to just a couple of times per day.

Do you think catching them before cleaning the tank could have been a factor and stressed them out too much?

The only things I did to the tank in the last 2 days was add a new heater, do a water change, stir up the sand before syphoning.
Are there any poisonous gases in the heater vacuum that when it cracked could have leaked into the water?

Also I've noticed that the water has gone quite cloudy in the last 24 hours since the fish started dying, is this a sign of bacteria? The tank has got an awful smell to it now too.

 

[weezawoo]

thats so sad to wake up to a dead tank!

Im not sure but there may have been something in the heater. Can't rule it out!

Also there could have been gases in the sand when you moved it around that were harmful.

I would reccommend less sand to keep it cleaner.

With mine I just left them in the tank once I moved them so it might be that it stressed them.

The tank is probably cloudy because of bacteria from dead bodies tbh. I would take everything out, even the filter media if you can. When you have another batch just take the media from the main tanks filter. I also use tank water to add to the fry tank and use that for w/c although others may do differently.

The first couple days they eat their egg sacs so no need for feeding. Just be careful with the amount of food you give and hopefully should be fine.

I didn't provide plants it was an empty tank with heater filter and small bit of sand but I did hide it in the cuboard under the tank so they were chilled out! Light on for few hours a day.

Hope you have more luck with the next ones!

 

[scotty]

with stirring up the sand,it could be possible that it caused an amonia spike

 

[ChemEng]

Thanks for the replies. Everything has had a really good clean out and lets hope I have more luck next time.

There are too many factors in their deaths imo so it's hard to pin point exactly what it was. Having less sand and feeding less is a good start to preventing it happening again though.