Tropical fish

[Dancer38]

Hi. We purchased a 25litre tropical tank last Saturday. We heated it to 27 degrees as told and put in the water purifier. The water was so so clear, so on the Wednesday we purchased 4 black neon tetra and 4 assorted Platy.
We followed instructions, got them used to the water before putting them in the tank. 1st day they seemed fine and happy. Yesterday we noticed they were gasping at the surface. We read this is due to lack of oxygen so followed instructions and change 15% of the water (cleansing it again) too allow more oxygen in.
We woke up this morning and they were all dead.
I don't know what we did wrong as we followed all instructions given.
We are gutted and so sad for the fish. We just wanted to give them a good home.
Any advice greatly appreciated or if anyone has experienced this as well.
Thanks so much

 

[Aiken Drum]

There are so many things that could have gone wrong. The most likely things to kill fish that quickly.

- The fish where already sick.
- Chlorine. You say you used purifier. What did you use exactly?
- Moving fish between very different water parameters/didn't acclaimate properly.

A few other things to point out, but they are unlikely to kill fish in that short a space of time.

- Its highly unlikely you cycled the tank. Do you know anything about the nitrogen cycle or how to cycle a tank to make it safe for fish?
- In an uncycled tank, that is a lot of bioload for such a small tank. Your water parameters would quickly get toxic with no cycle.
- 27c is very warm for those fish.

Edit: You didn't mention a filter. Do you have a filter?