Dwarf Gourami Help

[Tankless]

When the substrate hasn’t been touched for a while, I assumed there would be a build up of harmful gases? Then I would’ve had dead shrimp however there was no issue with them.

I have a Chihiros skimmer and my lily pipe outflow is in the same position as it has been since I last rescaped at the beginning of the year. My drop checker holds fairly steady at light green during the photoperiod as I don’t like injecting until lime green plus the majority of the plants I use are in the easy to medium category. Other than the front right (which I haven’t touched), the substrate has had a deep clean over the last two weeks when I thinned out the plants. Filter was cleaned on Tuesday or Wednesday.

 

[Tankless]

I’ve now lost 7 of my 11 black phantom tetras. Number 8 is on deaths door. The sequence is as follows:
1. Difficulty in swimming (hovering near the top of the tank)
2. At the top gasping
3. Death

The first 6 were purchased in September and then I added another 5 in December. I haven’t lost any of the other fish (Espei Rasboras, Bristlenose Plecos, 2 Ember tetras which are 6 years in age, 1 Zebra Loach) or any shrimp/solo zebra nerite. They all are as per normal.

I have no idea what it could be, I might dose esha 2000 as that’s the only medicine in the cabinet or I accept that I’ll probably lose all of the Black phantoms.

Pictures of number 8 which will probably die soon.

 

[Bradders]

Hmm - what's the white stuff on the right side of the fish? Is that some camera trick of the light or something else?

 

[Tankless]

I think it’s just the camera, fish was moving and the phone wasn’t focusing too well.

 

[Bradders]

Ah, OK. Good stuff! Same for these specs?

 

[Tankless]

The little white bubbles would either be the co2 or twinstar nano plus bubbles. It’s in the direction of the outflow path. If that’s what you’re referring to. No white dots on the fish.

 

[Bradders]

Ok, thanks. I am really at a loss. I am so surprised that this has affected one species of fish and not the others.

On the surface, it looks like some oxygen deficiency, whether caused by a parasite in the fish or environment. Assuming the environment is OK, then it must be pathogenic. But that does not explain why just this type of fish.