Dwarf Gourami incredibly ill, later euthanised. What illness?

[triivk]

Hi, my fish have just undergone an incredibly stressful passing of one of their tankmates - and I was needing help on the cause of the death.

I have a 250 litre tank, well established.
PH: 6.7ish
Nitrate: 0.05ppm (if that)
Nitrite: 0ppm
Ammonia: 0ppm
GH: 0-5ppm
KH: 0-5ppm (I am really unsure on how to boost this so perhaps it contributed?)
(Heavily planted, 20-25% water changes weekly, canister filter + heated tank)
I have 4 dwarf gourami, and although they have a fraught relationship from time to time, they're only defending their various nests. This particular dwarf gourami had been losing colour quickly, frequent issues with bloating, and black/discoloration on fins. Until today, he was active, swimming a lot, instead today he was sitting on the bottom of the tank, where I moved him to a quarantine tank and settled him in a net near the top of the water to be able to get oxygen.

He soon became entirely unresponsive, though still alive, so I quickly moved him to a container with clove bud oil, where he passed (however is still sitting in as a precaution).

I will attach some photos, and I hope you all might be able to aid in the identification/or even if this 'disease' or otherwise will be a threat to my other DG. (I'm new-ish to fish keeping, and as being 15 this is majorly stressful. Please attach any advice, I'd really appreciate it)

 

[Aiken Drum]

Can you give some more detail please. How long have you had the tank? How long have you had the fish? How old are they? What is your normal water change schedule?

Dwarf gourami disease is a possibility.

Im going to say your water parameters are essentially impossible. The only way you can feasibly see nothing is if you did your water test immediately after a 100% water change and you are essentially water straight from the tap. Nitrate is the end product of the nitrogen cycle. In a cycled tank you should see nitrate. In an uncycled tank you should see ammonia and or nitrite depending on how far progressed your cycle is. Seeing nothing is a good indication something is wrong with your testing, which could indicate a water quality issue you arent aware of.

What test kit are you using? Make sure you are doing the tests correctly, maybe get a 2nd opinion on your test results. Im not sure how anyone can arrive at nitrate of 0.05ppm when most tests lowest positive test result is 5ppm.

 

[triivk]

(I don't know how to work threads but here is reply)

Can you give some more detail please. How long have you had the tank? How long have you had the fish? How old are they? What is your normal water change schedule?

Dwarf gourami disease is a possibility.

Im going to say your water parameters are essentially impossible. The only way you can feasibly see nothing is if you did your water test immediately after a 100% water change and you are essentially water straight from the tap. Nitrate is the end product of the nitrogen cycle. In a cycled tank you should see nitrate. In an uncycled tank you should see ammonia and or nitrite depending on how far progressed your cycle is. Seeing nothing is a good indication something is wrong with your testing, which could indicate a water quality issue you arent aware of.

What test kit are you using? Make sure you are doing the tests correctly, maybe get a 2nd opinion on your test results. Im not sure how anyone can arrive at nitrate of 0.05ppm when most tests lowest positive test result is 5ppm.

Admittedly I had used a stick test for those earlier readings, which have inaccurate results at the best of times. Now, as I double check with the API freshwater master test kit,
Ammonia: 0ppm
Nitrite: 0ppm
Nitrate: 15ppm (apologies for the unchecked results before)

So yes, nitrate is potentially high? However none of my other fish are afflicted in the way that this one DG is. I have had the tank running for 3months-ish, it cycled after 1 month, however all fish were present in tank during cycling (managed by multiple water changes per week, alongside water treating to detoxify ammonia). Unfortunately I am unsure of their age. They are fairly large in size (as seen in the pictures) however no information was provided by the store I bought them from. I change the water weekly, or according to test results. I have issues with flow from my canister filter and so will often squeeze the muck on the pre-filter into the bio-media in the actual filter. (I don't know how else to fix flow issues, as this seems to work). Tank is consistently at 24-25degrees Celsius.

In the tank, there are 4 dwarf gourami, 3 emperor tetras, 3 buenos aires tetras, 6 neon tetras, and 1 chinese algae eater.
(I am aware that the emperor and buenos aires tetras are better to have in larger groups.)

Are my KH/GH too low? What do those results mean? Thank you heaps for your response.

 

[Aiken Drum]

Nitrate at 15ppm is fine.

Your water hardness isnt an issue. A bit low, but fish adapt to a wide range of water parameters. If you obtained your fish locally they will have been raised and kept in similar water to what you have. If you really wanted to raise both those parameters a piece of cuttlefish bone in your tank or filter, or a bag of crushed coral in your filter will add both calcium and carbonate to raise both GH and KH (and pH).

Do you know the sexes of your fish? Too many males could be stessful and stress causes all sorts of health issues. With 4 gouramis 1M/3F would be your best mix.

Unfortunately fish dying is part of the hobby. In your case i think all you can do is keep an eye on your remaining fish.