Green neon tetras dying one by one

[bwc_nothgiel]

Hello - I recently ordered 10 green neon tetras from Aqua Huna to be put in my planted 20 gallon tank, and to my dismay they have been dying about one or two each day.

Over the course of around a week I am currently down to three left. Some seemed to have passed rapidly and I've only discovered them at the bottom of the tank. Others have had what appeared to be swim bladder issues, they couldn't quite navigate accurately, and eventually deteriorated to sinking to the bottom with little movement, and then expiring. The last had it much worse where they were swimming extremely erratically in a corkscrew pattern with essentially zero coordination. For each fish I found not doing well, I separated them in a small make shift quarantine tank to hopefully destress them, but in each case they passed away, even with mixing in new clean treated water in the last couple. The fish first appeared fine, these symptoms appeared to come from out of the blue. The fish are around a half inch in length.

Unfortunately my tank hasn't made a full cycle. When I first added the fish, I also dosed the tank with FritzZyme 7 and thought that would be a safe jumpstart, a mistake I now realize after heavy research. I have been testing the tank a ton and the parameters have not changed from these:

Temp: 78 deg F
ph: 6.8 - 7.0
Ammonia: 0ppm
Nitrite: 0ppm
Nitrate: 0-10ppm
Chlorine: 0 mg/L
GH: ~75 mg/L
TAL: ~40-80 mg/L
KH: ~40 mg/L

I've made a few 25% water changes just in case to rely on the dechlorinator to detoxify the water, but it hasn't appeared to help. I am stumped now as I have always measured zero ammonia and nitrite. Aren't those the problem chemicals in an uncycled tank? I wonder if the health issues were there already in the suppliers care? The corkscrew swimming behavior sounds a lot like whirling disease. My other hunch is the tropical flake I am feeding is causing them to bloat, starting today I will try fast them a few days.

I am gutted by the loss of these fish. I will keep fighting for those still left. I am open to any ideas to save them!

[Aiken Drum]

As you have pointed out, while your tank may not be cycled, the water changes you are doing is keeping the water safe. So i don't think the issue is your tanks cycle.

You are right, the issue might be from the supplier or from shipping. Water parameters may have got pretty bad during shipping and this is manifesting by deaths over the days following on receipt.

How did you acclimate the fish before adding them into your tank?

What may have happened is ammonia elevates in the bag over time. The water is starved of oxygen, and pH drops. At low pH the ammonia is non-toxic as it will be ammonium. During your acclimating, you open the bag and O2 rises, pH rises. That ammonium reverts to ammonia and suddenly becomes toxic. Result, fish dying over the following days/weeks. This will all be down to how long fish are in shipping. In these instances, getting the fish out of the water they have been transported in immediately after the bag is opened is beneficial so they arent sat in the ammonia they produced during transport.

Re: Cycling your tank. Are you sure your tank isnt cycled?

Are you seeing ammonia prior to your water changes? If not, you may be cycled. If you arent cycled and the amount of water changes you are doing is essentially keeping ammonia at undetectable levels, your cycle will never establish as the bacteria are being starved of food. While keeping water as clean as possible will be beneficial to the health of your struggling fish, you will at some point need to elevate the ammonia to some degree over a period of time to get your cycle established.

[bwc_nothgiel]

The travel time to me was 3 days.

I acclimated the fish following their included instructions:
15 minutes floating sealed bag in tank to temperature acclimate

Transfer entire bag to container, take ~50% of current container volume's worth of water from tank and mix with container. Wait 15 minutes.

Then repeat the above step again, another ~50% of container's worth of water from tank into the container. Wait 15 minutes. Then finally transfer the fish into the tank.

Dang - I never measured the water they came in, but it did seem rough. It was yellow in color and it did not smell pleasant. I do recall hearing lower temps and ph will have less toxic ammonia and as those parameters go up the worse effect the ammonia will have. Would the better option have been to temperature acclimate, open bag and immediately transfer? Or get the bag open immediately and transfer?

For cycling I am not 100% sure. I definitely have not measured any ammonia or nitrite at all throughout all of this. I agree I may have kept the levels at low with my changes. I changed the water out of pure panic. I also wonder given how small the fish are, if they are putting a very light load on the tank that would take a long time to show.

Today I still have 3 hanging on. They seem to be swimming fine. They were already shy when they arrived, but now with 3 they are more on edge.

Thank you for the help!! I have been all over the place with what could be going on. With the ones that I quarantined they did seem to have very red gills, but just red, no dark purples or anything - but it seems to support ammonia exposure.

I think I have a plan moving forward. I will stop with water changes and keep testing the water to get an idea of where the cycle is at. I will try feed tomorrow and will soak the flake a bit beforehand to hopefully allow it to be digested better. I think I will makeshift a tub and try cycle some media in there as a backup plan. Thank you again!!

[Aiken Drum]

A better way to acclimate fish that have been in transit for an extended period would be to float the bag sealed to temperature acclimate.

Get a fish net and sit it over a bucket. Open the bag and immediately pour the water and fish into the net. Water drops into the bucket, fish get caught in the net. Transfer the fish to your display tank. This way the fish are not subjected to any ammonia and its toxicity as pH rises.

This is how I acclimate fish, although i get my fish locally and they only have a 20 minute journey.

[bwc_nothgiel]

Quick update:

I still have the three green neons! They have overall been doing good and eating well. My plants are thriving as well and they have much more cover to hide around in.

I still have not measured any ammonia or nitrite in the tank. I even let off water changes for a little over 2 weeks. The tank got dirty and grew algae, but ammonia/nitrite levels never went up. I think what is going on is the three small fish have a small ammonia output that is leading to amounts too small to be measured. Along with that, I learned that plants also uptake ammonia and nitrite. I think they have played a role in keeping my levels down.

With that all seems to be looking up. I am hoping to add more green neons very soon to get them back to schooling numbers so that they can be more comfortable.