Is it a Corydora Thing??? What is going on??

[Sandra the fish rookie]

Hi Everyone, 

I am back! I had a rough year, unexpectedly lost one of my dogs and lost my "mojo". I had set up 2 20 Gallon tanks(20G high, 20G long) before he died, and left them for over a year... just plants. I have a seasoned QT tank on the go at all times, as I have 2 main display tanks (40G breeder, 20G high) full of healthy community fish. 

I decided it was time to fill the other tanks. the 20G long, I got Habrosus Corydoras (10) knowing they tank was cycled, and there was NO other life in it (bladder snails) I put them in there. and QT right from there. they did GREAT (I am obsessed with them actually).

I LOVE Corydoras's and they are in ALL my tanks. I have never had ANY issues with QT, disease ect. Still have the originals for over 3 years, and they are breeding. 

So, I decide I was going to go to my LFS and get the following 1) lemon long fin pleco (that is SUPER SMALL), 10 Julii Cory's, 5 Guppies (I just got additional to add to my outdoor pond only) and 2 albino corys (to add to my existing ones in the 20G again REALLY SMALL). It's a 10G QT Tank, with 2 sponge filters, and an HOB filter full of sponge. I have had WAY more than that stocking in that tank before, and it handled it NO Problem.

I was concerned about the size of the pleco and albino cory's because they were WAY smaller than I have purchased before but took a chance. 

Purchased Saturday, everyone was fine, derpy, eating blood worms, and looked fine. Pleco was eating his wood, and got to work on the walls, and surfaces of the tank. 

Sunday albino cory and 2 guppies dead. Tested my water, PH 7.3, Nitrates 15ppm, Nitrites 0, Ammonia 0, GH 250ish (I have very hard water here in NC), and KH 50ppm Temp 78 degrees. I don't usually start the QT meds till a week after they have adjusted, I feed them well, and watch them. Then week 2 meds are in!

Sunday night, 1 Julii dead (water change), Monday another Julii dead (test water results are same as above), Tuesday another Julii dead (I do a water change and start meds because I don't know what is going on), today Wednesday another Julii dead. Now my water is a mess, it is having a bacterial bloom and now have a "trace"10 PPM Nitrate. I do a water change, add some Fritz zyme (because I had some on hand). I have NEVER had death like that EVER! I am not a "rookie" but have had fish now since 2019/2020. I struggled with guppies initially, but I have had no problems since purchasing them online and getting mutts.

The Pleco is fine, the rest of the guppies are fine, the one small albino which appears to be okay, but the Julii we will have to see. It's the first time I have this breed of cory and not sure if they are just more sensitive? Right now, they are huddled together in the corner. 

I watched the video and talk about the accidental poisoning and took precautions. Not sure if this is the issue. I looked at the bodies, and I can't see anything. See pictures below:

[nabokovfan87]

4 hours ago, Sandra the fish rookie said:

I LOVE Corydoras's and they are in ALL my tanks.

Me too! 🙂

I'm very sorry about the loss of your pups.

4 hours ago, Sandra the fish rookie said:

Sunday albino cory and 2 guppies dead. Tested my water, PH 7.3, Nitrates 15ppm, Nitrites 0, Ammonia 0, GH 250ish (I have very hard water here in NC), and KH 50ppm Temp 78 degrees. I don't usually start the QT meds till a week after they have adjusted, I feed them well, and watch them. Then week 2 meds are in!

A lot of times corydoras can have a tough time with acclimation. It isn't a hard and fast rule, but the general guide is that corydoras like cool water, they like PH around 7, and they LOVE oxygenation.  As water gets warmer it hold less oxygenation leading to stress. Stress, like acclimation, can cause issues as well.

Whenever you add meds it's often recommended to add additional air as well via an air stone.

4 hours ago, Sandra the fish rookie said:

The Pleco is fine, the rest of the guppies are fine, the one small albino which appears to be okay, but the Julii we will have to see. It's the first time I have this breed of cory and not sure if they are just more sensitive? Right now, they are huddled together in the corner. 

I watched the video and talk about the accidental poisoning and took precautions. Not sure if this is the issue. I looked at the bodies, and I can't see anything.

Yeah, I don't see anything either. One thing to keep in mind is the "be the fish" mindset. Essentially, trying to understand what they are saying and asking you for. They are huddled in the corner, maybe they just need a certain kind of decor or something. That is where they feel safe, where the light is dimmer, or that's just where they have more flow and water circulation.

It's always a bit tough to get corydoras into my tanks for me, but when I do it's been such a rewarding fish. I would love the challenge (not negativelyin any way) to bring in another species to my tank I just setup and to be able to use all the knowledge I have now.  I learned a lot over the years about their care and what they prefer.

Ultimately whenever I see issues I double check air and temperature. During the summer here my tanks get a bit too warm for comfort for them, but they always have been such a rewarding fish to have.

I hope we can get things moving in the right direction for you.

As far as any advice to help out.... I will have to get some coffee and dive into guppy care. I don't think the temp is out of the range for anything. I think 78 is fine. 76 might be a better setup long term. As far as species in that tank, I highly recommend the false Julii (or true Julii) Corydoras as they take time to get a full pattern, but when they do it's magnificent! They can usually handle 78 degrees a bit better than something like a panda Cory can.

This video might be helpful as well to explain what's going on for the fish.

 

All of your water seems fine. You did add a lot of fish at once and that definitely could lead to a spike. Less is more. But hopefully the next attempt goes a bit better for you.

I try to only bring in one species at a time. Maybe that will help to slowly keep the water parameters under control if there is any sort of ammonia issue we aren't seeing.

How did you acclimate the fish from the store?

[Comradovich]

Those nitrates aren't likely to be your problem. You can keep water changing to fix it, but I'm doubting that lowering it is going to be much help to you. By way of example, I run a planted tank that regularly has 15-20 ppm when I test, and I'm adding nitrate fertilizer to it to raise that amount so I don't start losing plants. Fun fact: those of us with planted tanks tend to avoid mentioning our nitrate levels to fish keepers who don't, because all those shocked gasps get old quick.

Adding so many fish at once is a stressor on all of the fish. (You may want to go for closer to 2-3 at a time). Main thing is you're adding something that's already feeling stressed, to a tank with an established pecking order, which just adds stress to everything else. This stress leads to either the fish getting "stress ick", or getting weak enough from stress for regular "ick" to set in. This is why the quarantine med treatment is suggested in YT vids, (I seem to remember you mentioning a med trio). The other problem with adding many fish at once is that your biological filter has to catch up to the sudden increase in bioload it has to process. It does this by breeding bacteria, which is why there's usually a lag between adding fish and getting your parameters back to the usual balance when you test. I'm mentioning this because I suspect you'll be looking at a relatively minor disease outbreak soon, and you shouldn't panic if you're already planning QT meds. This is probably not your cory issue, I'm just being proactive.

What I suspect is your issue is self-poisoning. Julii's have venom glands. Your albinos are Aeneus, most likely. I can't remember if they also have venom or not. Point is that corys with venom are not immune to their own venom. While this sounds like a stupid evolutionary trait, you also have to remember that these are shoaling fish. A given cory isn't dumping venom to save himself, he's making sure that his predator remembers fish of his type as the guys that put said predators entire face to sleep for the rest of the day. That way, it leaves the rest of the shoal alone.

Here's a story from one of the YT livestreams that happened over the holidays... (I want to say this is Rikostan's story, but I can't quite remember, I think it was one of Chattanooga Ed's streams):

So, fish keepers go to a shop during one of their convention visits. They see these neat corys they definitely want to bring home. Shop employee starts netting corys, one or two get stuck in the net. As they're putting them into the catch cup, they notice the catch cup water is slightly cloudy. Shop employee bags up the corys from the catch cup, and starts ringing up the corys. Bag water is definitely slightly cloudy now. Fish keepers notice at this point that some of the corys aren't moving. Get them back to the hotel, corys start dying. What happened? Well, getting stuck in the net broke or snagged one of the corys' venom spines. It panics and dumps venom. Other corys get stressed and also dump venom. Everyone in the bag is now slightly poisoned. Since they're already a little weak and stressed from the supply chain getting to the store itself, venom doesn't help at all.

How do you avoid these deaths? You use new water for the bag from the shop RO system or a QT tank. Catch cup water gets tossed. This minimizes the amount of time a given cory spends in water that has been envenomed. You also don't dally on the way home from the shop. You want to minimize the amount of time a cory spends in a bag where it might panic. If you have kids, you don't let them look at the bagged fish on the way home. Because to a cory, it's like Godzilla just started peering in to find a tasty treat. When you get home, you want to assess the bag before you decide on how to acclimate. If the bag's got cloudy water, skip straight to "plop 'n drop". Cory will take less stress from a sudden change in temp and ph than it will from sitting in its own venom. Maybe temp acclimate, but you don't have time for drip acclimation if that cory already dropped venom.

You however, are past this stage. Save those little nuggets above for future shop runs. You did two water changes since the Corys hit your tanks, so they're probably out of any venom they may have dropped. Whatever filter you're using probably got rid of it. You may want to google "Corydoras self-poisoning" just to check if there's anything else you could try, but you should mostly be in a mode of making them as comfortable in the new tank as possible. What I would suggest instead is get this colony of Julii and Albinos healthy, and if you decide you need more of these particular fish, see if you can't spawn them yourself. That allows you to skip any supply chain or shop mishaps. What's happening to your fish is a combination of venom and stress, you kind of just have to ride it out.

Body count is 5 Julii, 1 albino, and two guppies? I mean, the Julii decimation isn't a stunning result, but you didn't know any better. Albino Aeneus and Guppies are pretty hard put upon in shops, that's a relatively normal outcome. I definitely wouldn't beat myself up over this episode. I would definitely make plans to spawn what's left, though. You didn't pick up the final outcome for your tanks, you picked up the building blocks to get yourself to that final outcome. You can totally recover from this.