my guppies die with rotten fish tails and scoliosis

tallguytelli said:

Everything was fine until I went away for 15 days last year. I used an automatic fish feeder which I think worked fine. just Before my trip, I changed the water. And I had added a new guppy before my trip.

After my return, every week or 15 days, I have lost one or two guppies. As it is seen in the pictures, they have certainly have rotten fish tails and scoliosis before they die. scoliosis is not because of breeding and fighting and it’s not hereditary. They come together and fish die.
My aquarium is 120 liters and contain(ed) 50 guppies. Like I said everything was fine for a long time until my trip and before adding the new guppy. They lived together fine and with almost no deaths. I cared well now and then.
It has been 9 months and I couldn't find a solution for this problem. I regularly change water. I feed them with quality food. I tried some antibiotic and other medicine (not in the main tank) with no effect. When I see a fish with a problem, I take it to another tank.
I am almost tired now and afraid to look at the tank. Can anyone understand what’s happening and advice me something?

View attachment 32115

Click to expand...

tallguytelli said:

Everything was fine until I went away for 15 days last year. I used an automatic fish feeder which I think worked fine. just Before my trip, I changed the water. And I had added a new guppy before my trip.

After my return, every week or 15 days, I have lost one or two guppies. As it is seen in the pictures, they have certainly have rotten fish tails and scoliosis before they die. scoliosis is not because of breeding and fighting and it’s not hereditary. They come together and fish die.
My aquarium is 120 liters and contain(ed) 50 guppies. Like I said everything was fine for a long time until my trip and before adding the new guppy. They lived together fine and with almost no deaths. I cared well now and then.
It has been 9 months and I couldn't find a solution for this problem. I regularly change water. I feed them with quality food. I tried some antibiotic and other medicine (not in the main tank) with no effect. When I see a fish with a problem, I take it to another tank.
I am almost tired now and afraid to look at the tank. Can anyone understand what’s happening and advice me something?

View attachment 32115

Click to expand...