What's happening to my Lemon Tetras!? Disease?

[quinnARIUM]

Hey everyone,

I have had 10 lemon tetras in a 20 gal quarantine tank for about three months while I was setting up their 75 gal. They were completely healthy in there and grew a ton!

Then, about 4 days ago I finally moved them into the big tank. The big tank had only been set up for about 2 weeks but I used a bit if old media and I needed to get the quarantine tank empty for some new fish. I did a 50% water change before I added the Lemon Tetras. I acclimated them pretty well and they seemed immediately comfortable. Then, three days past when I first added the Lemon Tetras, one tetras showed up dead. And I had "just" purchased 8 Corydoras and five otocinculus for the tank! Stressed out I quickly did a water test. The results were:
gH: 10-15 mg/L
Nitrate: 15 mg/L
Nitrite: 1 mg/L
kH: 20 mg/L
pH: ≈6.6?
This was actually my first time testing my aquarium water. I was surprised by how acidic my water is, but pH swings don't seem to be the problem since I checked again in the morning and the pH was the same. After testing the water I noticed a lemon tetra seeming to gulp for air and float aimlessly around the tank. He died about 20 minutes later. My first though then was oxygen deficiency, but with only 10 lemon tetras in a 75 gal full of plants and with strong surface agitation, I deemed that unlikely.

I added the Corydoras and otocinculus (I had no wear else to put them) and they seem fine so far.

But this morning-- I kept an air stone in the tank overnight to be sure, another Lemon Tetra was floating around aimlessly. I have noticed a bit of aggression between the school, but the tetra seems unharmed. Now he is quickly opening and closing his mouth at the surface.

Any thought would be helpful! Please send any advice! Has anyone had experience with Lemon Tetras?

 

[quinnARIUM]

Here is a picture of the confused lemon tetra and the rest of the school:

 

[Essjay]

Nitrite: 1 mg/L

Nitrite needs to be zero.
It looks as though you are using strips to test and they don't include ammonia, so the ammonia could be high as well. It is always advisable to have a separate ammonia tester as that's the first thing to show up when things go wrong.
You need to do a water change asap to get the nitrite down to zero.
The good news is that with a pH of 6.6, any ammonia in the water will be in the non-toxic ammonia form.

It sounds as though the tank was not actually cycled.

 

[Byron]

I had a group of Lemons for several years; they spawned so readily and some of the fry managed to survive to the extent that I gave some 60 Lemons to a local store.

Anyway, there is nothing wrong with your water parameters (GH, pH). The pH will remain acidic because of the low GH, and this suits the fish mentioned. Do not acquire any hard water species (all livebearers for example), just so you know.

The respiration at the surface does indicate something wrong in the water though. I won't guess as to what, other members may have suggestions--but as it has been only two fish, it is possible they received some form of internal damage when they were netted and moved; I have had this myself, sometimes these little tetras can get between the net and the glass and it doesn't take much.

But I would do a major water change immediately, 70-75% of the tank's volume at one change, and use only a conditioner in the fresh water. BTW, which conditioner do you use?

Increase surface agitation by positioning the filter return to achieve this.

DIT. @Essjay posted as I have been typing, and fortunately picked up the nitrite...but with live plants that you mention, I would not expect this. I still suggest a major W/C and monitor.

 

[Slaphppy7]

+1 to the above, nitrItes are poisonous to fish, and if you have them, you have ammonia, as well, which is also poisonous.

Get an API Freshwater Master test kit, some good conditioner (Seachem Prime or API Tap Conditioner), and do a large WC ASAP.

 

[quinnARIUM]

Ok, I will do a water change right now. The tank was not fully cycled but I thought I could keep on top of the water changes to keep nitrite and ammonia at zero. I wasn't able to test for ammonia but sounds like it is good news that my pH is low! Is nitrite at 1 mg/L actually lethal?

 

[quinnARIUM]

I use Tetra AquaSafe Plus by the way. And the chlorine content in my water is very low. Is chlorine actually dangerous to fish? I though it just destroyed beneficial bacteria populations?

 

[Essjay]

Nitrite does to fish what carbon monoxide does to us. It binds to the oxygen carrying sites on red blood cells and stops the oxygen attaching. So like we are not killed immediately by low levels of carbon monoxide but it makes us sick, the same thing happens to fish.


Chlorine does irritate fish's gills and skin. But any water conditioner should remove chlorine.

 

[quinnARIUM]

Ok thank you for the helpful feedback! I think you guys are probably right about the tank not being cycled being the problem. The Lemon Tetras were used to an "extremely" planted and established aquarium where I am sure the water quality was good. Putting them into the large tank where nitrite is present shocked some of their systems. I just hope the rest of the fish are going to be okay ?