1. I recently started trying a new food which they didn't seem to take to as well as the previous one, I left instructions that they be fed this 3 times while I was away, they didn't eat much if any of the food, which was decaying in the tank when I returned. Next time, I will not leave instructions to feed any larger fish while I'm away, they will be fine for a week or two without food. Maybe just a small pinch of flake for small tetras to keep them going once a week.
2. The flow from the filter (air powered HMF) was very slow when I returned, the same for the air driven sponge filter, I should have cleaned these before I left, and with the decaying food maybe there was an issue with low dissolved oxygen in the water, due to the significantly reduced flow.
3. From looking at the faeces a while back I thought they may need to be wormed soon, but I kept putting it off, maybe this didn't help when combined with the other factors above.
4. I noticed a yellow oily like substance, in some of the caves and floating on the water, maybe fats from the fish decaying, maybe something else? I've not seen this before, there is a picture below.
I tested for Ammonia, but found none, I was expecting to find some, the smell wasn't great, after that I didn't perform any further tests.
One fish, I believe the female, was in a worse state than the others, had maybe been dead for 2-3 days, very swollen, with eyes popping out, I guess this further contributed to the loss of the others, who only showed very early signs of swelling. The one with the hollow looking stomach in the pictures below is the one which was most swollen but deflated while I was removing it from the tank.
The young look great, so I will concentrate on raising them for now, hopefully they will breed in a year or two once they put on some more size.
- Yellow oil like substance floating on the water
