Fish Constantly Dying

I am not completely new to the hobby. I have had my tank for almost a year and a half but have had a consistent problem that no one at any store has been able to solve. I have had dozens of fish over the year and a half die within the first 24-48 hours of being introduced to my tank. This represents probably about 80% of all of the fish I have had. Seemingly at random, some fish live and are fine, but most others don't make it past two days. At one point I had one of my original tetras who survived for months while every single other fish I would introduce would die. Right now I have 7 fish alive and well. They are all tetras. I have introduced many different types of tetras and many other species and they basically all die. I just added two gourami's yesterday. They were both fine when they entered the tank but now, a little over 24 hours later, they are both at death's door. The seven other fish are doing fine.

I have tested the water multiple times and I have brought water samples to my local shop multiple times and no one has any idea why so many of the fish keep dying so fast. It is not an aggression thing either because there is absolutely no sign of that. I do water changes, treat the water, keep the tank clean, etc. There has been nothing that has helped.

It is BEYOND frustrating to keep losing them and having no explanation... and to have this going on for almost a year and a half! Any suggestions on what could be going on and how I can fix it would be GREATLY appreciated!!

What are the water parameters?
How often do you do water changes and how much do you change?

Additionally, what does your introduction process look like?

In addition to the above, what is your tank setup like? What substrate and decor do you have? Live plants? Size of tank? What do you treat the water with? Do you add co2? Are you using tap/well/RO water? I'm sure with more information people may be able to help, but for now perhaps don't buy any more fish until you have some ideas on what might be causing it.

Thank you for the responses so far. All of the water tests come back good and always have. pH, nitrites, nitrates, chlorine, ammonia, etc. I will do water changes every few weeks or so and change out about 25-30%. I have done larger changes in the past as a possible remedy to my problem but that has not yielded results. All of the water is coming from a municipal water system. All water that goes in the tank is treated with API Stresscoat. I have also used another brand of water treatment as well and that did not fix my problem. I do not add co2.

I have a 29 gallon tank. I have gravel substrate in the tank. I do not remember the brand but I bought it at my local store. Only artificial plants are in the tank, nothing live. I have a bubbler going in the tank as well.

My introduction process is to float the bags in the tank for maybe 20-30 minutes. After that time I have tried both cutting the bags open and letting them swim out as well as just dumping the fish right out of the bags. I have tried different things to see if they would help my issue but I have found no correlation in how I have been introducing them and if they survive.

I think the strangest thing about my issue is that there will be a group of fish, like I have right now, that survive and seem perfectly fine all while new additions will die within a day or two. One of the two fish I added two days ago was dead this morning and the other one looks like he will be going by the end of the day.

I hope that information is helpful. I'm desperate!!

Not sure what you mean by "always have. pH, nitrites, nitrates, chlorine, ammonia, etc." You should have 0 ammonia, 0 nitrites, 0 chlorine, and lower nitrates- 40 ppm is my personal max (others may feel differently).

I change my water weekly on my bigger tank. I would suggest a 50% water change each week. The water parameters can help determine the best frequency- if the ones that should be 0 are 0, then look at nitrates- change the water before it starts to rise to a point that's bad. You want to stay ahead of bad situations.

The other big thing is filtration. Make sure you have good bio-media as part of your filter. If you use sponge filters, the sponge is very good for bio filtration. Don't clean it often, and if you have ammonia or nitrites, don't clean it at all until you get a point were there is 0 of each- look up cycling a tank to see more.

I use a cannister filter with K1 filter media- just little plastic things with lots of surface area. You'll see all kinds of opinions on the best bio-media, but having it in the filter is the most important thing.

Also, if you have a hang-on-the-back filter, don't change the cartridges regularly like they suggest. Let them sit- the good bacteria has to grow.

Also, different fish need different parameters. For instance, neon tetras, a lot of folks' immediate go to for first fish, need a very clean, seasoned tank with well-established beneficial bacteria before they will survive. Look for descriptions of each fish you're considering and make sure you get the right number if they are shoaling fish and make sure your parameters are within the range for the fish you want.

Don't trust what they tell you at the fish store- double check it. They are great folks, but they don't always know and their first job is to sell.

I can only sympathise with what you are experiencing.

what filter are you using? what temperature do you maintain your tank at? what test kits are you using? Do you know if your fish stores uses the same water supply as you?
photo of tank please.

I'm assuming that when you say the test results are always good that you mean zero for everything aside from a little bit of nitrate?

Please let us know your pH and hardness levels as well.

Do you know if the gravel is calcareous - chalk, coral, limestone based?

Is there ever anything like fragrance, disinfectant, furniture polish sprayed in the room?

Sotbas said:

Thank you for the responses so far. All of the water tests come back good and always have. pH, nitrites, nitrates, chlorine, ammonia, etc. I will do water changes every few weeks or so and change out about 25-30%. I have done larger changes in the past as a possible remedy to my problem but that has not yielded results. All of the water is coming from a municipal water system. All water that goes in the tank is treated with API Stresscoat. I have also used another brand of water treatment as well and that did not fix my problem. I do not add co2.

I have a 29 gallon tank. I have gravel substrate in the tank. I do not remember the brand but I bought it at my local store. Only artificial plants are in the tank, nothing live. I have a bubbler going in the tank as well.

My introduction process is to float the bags in the tank for maybe 20-30 minutes. After that time I have tried both cutting the bags open and letting them swim out as well as just dumping the fish right out of the bags. I have tried different things to see if they would help my issue but I have found no correlation in how I have been introducing them and if they survive.

I think the strangest thing about my issue is that there will be a group of fish, like I have right now, that survive and seem perfectly fine all while new additions will die within a day or two. One of the two fish I added two days ago was dead this morning and the other one looks like he will be going by the end of the day.

I hope that information is helpful. I'm desperate!!

Click to expand...

Which fish have survived? I think you said tetras, but what species?

Water changes would be my first go-to. I have a 29 gallon and change about 70% of my water every 7-9 days. Most people here would advocate for bigger, more regular water changes to start with. Water changes are your friend! Do you also dechlorinate the water with each change?

Real plants may also be helpful, I'm not great with all the complex ones but you could start with some floating plants such as water lettuce, elodea densa. You'd also need some liquid fertiliser, there are many brands out there, API, Seachem, a few others - everyone has their own preferences.

If you could take a picture of your test results and your tank too people may have some more ideas. Also try and find your area's water hardness and post that here.

You should really be changing water every week. I suspect the possibility of high nitrates. Which test kits are you using? Strips are unreliable, and liquid nitrate kits need bottle #2 banged a few times on a hard surface before the shaking, or they’ll start to give false results at some point.
Do you dechlorinate the new water going in?
And what are the numbers for your water parameters?

What sort of filter is on/ in the aquarium?
What filter media/ materials are in the filter?
How often do you clean the filter?
How do you clean the filter?
I assume the filter is run continuously (24/7).

Assuming the water has 0 ammonia, 0 nitrite, less than 20ppm nitrate, then we need to know the pH, GH (general hardness) and KH (carbonate hardness) in numbers.

Pictures of the sick, dead and healthy fish, and the entire tank might shed some light on the problem. It's highly possible you are getting sick or stressed fish.

What species of fish do you have and what types die?
If you aren't sure of the names, a picture will allow us to identify them.

Find out when the shop does water changes and when they get fish in.
If you are buying newly imported fish that have only been in the tanks for a few days, or the shop has done a water change in the last 24 hours, the fish could be dying from stress caused by going into different water.

The following link tells you what a lot of aquarium fishes go through to get to the pet shop. There's a significant amount of stress involved and it can be made worse if the new water (at your place) is different to the water the fish came from. This is why we need the pH, GH & KH in numbers. You could also ask the shop what the pH, GH & KH of their tanks are. And maybe ask the shop if they can ask their supplier what their pH, GH & KH are.

In addition to all of the above, if you’re adding a bunch of fish all at once (more than 1-3 at a time), it’s very possible you could be overloading your nitrifying bacteria by adding a large bioload all at once and then getting a bit of an ammonia spike as a result. This would be exacerbated by the fact that you don’t have any live plants, which can bear a lot of the brunt of ammonia uptake.

You say all of your parameters are “good”, but what does that mean? When are you testing? What are the actual values? You could be missing that little spike of ammonia or nitrites that’s killing your fish

Sorry I have not responded in so long and thank you for your responses. I have an Aqueon Quietflow filter on the tank and it uses the Aqueon carbon filters. I replace the filter cartridge every couple of months. The filter does run constantly, as does the bubbler. Right now there are a some different types of tetras in the tank.

I am using testing strips which I know are not completely accurate but the water has also been tested a few times at the store with a better testing kit and their results always have come back that things were within a good range.

When the new fish die I am usually only adding them 2 to 4 at a time. The last couple of times I have only added them two at a time since I am just expecting them to die. All of my 7 fish that have been in there for many months are still going strong and totally fine. Again, I have tried fish from two different stores at different times and have the same result... that is, except for the ones that are alive and well now.

I will attach a picture of the test strip that I used today. The pH reading looks a lit more red in the picture then it did in real life. It definitely looks in the neutral range.

Thanks everyone!

Sorry to add yet another question, but do they have any symptoms of disease or stress (gasping at surface, red-ish gills, etc.) before they die? Or are they fine and in the morning they are dead? Could help us to identify what's wrong.

Posting some full tank shots may be useful in helping us identify something you may be overlooking...you must be so frustrated