Tetra species tank urgent help!

[Skys54]

I have a 40lt fully cycled tank it has been running for four years and I clean it often and do water changes regularly. I have ten head and tail light tetras, two red eyed tetras, one black widow tetra, two Congo tetras and a neon tetra.

I've had a few of my tetras die over the last few months from various causes, but today I woke up and I have lost three more tetras one that had been showing signs of swim bladder trouble and to day I found him dead and two others in the same condition! Please does someone know what I can do? Will it spread to my other fish?

 

[coralbandit]

Without knowing for sure I would look to a bacterial issue if you are noting swim bladder issue..
What were some of the other causes or symptoms of other fish that passed before?

I would say to up water changes.

In general and ONLY IMO 40 liters and the stocking you listed sounds tight ,but if it worked well with even more for years then it is only my opinion...

Link to bacterial issues;

Bacterial infections | The Skeptical Aquarist

More symptoms may help figure stuff out.
The age of fish also...
If some of these fish are 4 years old you did alright by them IMO..

 

[jessipanda]

Do you have a water test kit? Like to see what the numbers are for your tank, especially ammonia.
By “clean it often” are you referring to the filter as well? If so, you shouldn't...that's where nearly all the beneficial bacteria (BB ) live which you need to convert ammonia from fish waste. Not sure if you know this or not, just a thought from what you said.
Also, I believe a 40 liter converts to around only 10 gallons, maybe 12. With that many fish, you might overstocked....what filter(s) are you running?
Another note, I believe tetras are schooling fish and prefer to be in groups of 6+ of their own kind (ex. neons with neons, congos with congos).

Whatever the problem may be, you should definitely test the water parameters and post them. It may help identify the issue, or at the very least the most possible issues.

Edit: coralbandit beat me here anyways; more experience than me

 

[Skys54]

Thank you so much for your help I did some extra research on what it could be and I'm taking a water sample into my local pet shop tomorrow as they can give me more actuate results. I don't clean the filters at all and I have found my filter to work perfectly the filter is actually rated from a much larger tank one hundred litters I think... Anyway I'm doing 25% water changes with pre treated water once every two days.

 

[scuba dude]

Getting water test is where I would start , great if a local store can test it but you need to be able to test yourself and monitor what is going on ( keep a log sheet) .
Invest in a basic test kit yourself you won't regret it. Test yourself and then if you need a second test then rely on your LFS for a second opinion.

 

[jessipanda]

Getting water test is where I would start , great if a local store can test it but you need to be able to test yourself and monitor what is going on ( keep a log sheet) .
Invest in a basic test kit yourself you won't regret it. Test yourself and then if you need a second test then rely on your LFS for a second opinion.

+1 get a liquid test kit. If you've had a tank for 4 years, it's definitely worth the investment and lasts awhile

 

[scuba dude]

+1 get a liquid test kit. If you've had a tank for 4 years, it's definitely worth the investment and lasts awhile

A little tip on the API liquid kit is the Ammonia and Nitrate tests can be doubled by filling the tube halfway to the recomended line and then cut the drops in half since both of those tests have an even number of drops ( 8 ammonia and 10 nitrate ) , not so easy with PH and nitrate since they have an odd number of drops. I guess you could measure it with a syringe and adjust accordingly but I have not tried that. Works fine for me with 1/2 a tube instead of a full one on ammonia and nitrates.

 

[jessipanda]

A little tip on the API liquid kit is the Ammonia and Nitrate tests can be doubled by filling the tube halfway to the recomended line and then cut the drops in half since both of those tests have an even number of drops ( 8 ammonia and 10 nitrate ) , not so easy with PH and nitrate since they have an odd number of drops. I guess you could measure it with a syringe and adjust accordingly but I have not tried that. Works fine for me with 1/2 a tube instead of a full one on ammonia and nitrates.

That's a great idea! Thanks for sharing that tip

 

[scuba dude]

That's a great idea! Thanks for sharing that tip

My pleasure!!