[Cthulhu]

12 days ago I purchased a dwarf gourami couple for my 25g. These are the first fish I buy in over 3 years.
When I put them in the aquarium (after proper acclimatation), the female was very active and showed every signs of great health. But the male acted like a zombie... moved slowly and not very active in general. Not long after that I saw them both scratch on plants, as fish do when they have ick.

I must say I didn't have time to choose the fish before the guy (who happens to be the manager) put them in the bag, but as I've always had excellent service and healthy fish from this place, I didn't think twice. No fish in the tank seemed sick, and the male he chose has nice color, so that was fine with me.

So I was concerned for the male, but he ate, not a lot but enough that I was confident he would get better. But then 6 days after I got them, he was very weak, mostly laying on his side, not eating, swimming a bit but usually to go get air at the surface. The next morning he was dead.

Meanwhile the female seemed in full health. Then I noticed something on one side/top of the mouth, looked like a scratch, so I figured it would heal by itself. But it hasn't, and actually looks a bit bigger now.

So I did a little search on fish diseases, but sources say different things about the same diseases. The one that seems most probable, if it's indeed a disease, is columnaris. As this disease seems to attack gills in particular, this would fit with how the male behaved in his last day.

I also see what seems like a pale spot on the female's anal fin. It could be early rot or could be perfectly normal, I can't say. But her behavior doesn't show any sign of distress, she has great appetite and is very active. She sometimes (rarely) go breath at the surface but it doesn't strike me as unusual behavior for a fish with a labyrinth.

Also, 2 ago days a lampeye killie died. Other than a 5 year old betta who died this summer, this is the first death in this aquarium in 3 years. I've had the killies for 5 years. Could be a coincidence but I don't like it.

None of the other inhabitants show any sign of problem. There are 9 lampeye killies, 2 corydoras, 6 amano shrimps and 4 dwarf frogs.

I always get my fish from this place, one of the most reputable fish store in Montreal, so 'm a bit surprised I would get sick fish from there. Doesn't mean it can't happen...

I don't know what I should do right now, if anything. I have absolutely zero experience recognizing and dealing with sick fish.


... As I'm writing this I jst noticed another killie dead. Too much for a coincidence, there is definitely something wrong.

 

[thelub]

My first go-to is melafix for strange illnesses. Its natural and I'm pretty sure its safe for all fish unlike some other medications.

Did you do a post mortem exam on the killie that died? Did it look abnormal in anyway compared to the others? Have you added anything to the tank since getting the DGs? It could also be a strange coincidence that the killies are dying. I don't know what the life span of a killie is, but it might be they are getting to the end of life stage and its just a coincidence.

 

[MSG]

I would NOT recommend using Melafix on gourami's or bettas.

Killifish don't have long lives, the ones you own should live about 3 years.

Regardless of how healthy fish are, you should QT the NEW fish before introducing them to an established tank. It might have been 3 years since you had an incident in your tank, but over the course of that time, a ton of fish have gone in & out of the tanks at your local TRUSTED fish store.

There's a possibility the gouramis have flukes/parasites.

Without photos, it's hard to guess what it could be based on descriptions.