The ammonia levels aren't high enough yet in just 2 days to worry about fish casualties.
Any fish that is used ina cycling of a tank will suffer very much. The hardiest will live, but they also have been through hell in the cycling process. The ammonia attacks the gill membranes of all fish and renders them either struggling to breathe or death.
There is no need to use any fish to cycle a tank. There is just no positive for it, imo. If anyone knows any positive for it, please let me know.
Not when you can use a fishless cycling and it will cycle faster, more stable and you can add the full compliment of fish when it's done. When you cycle with fish, the fish suffer and usually die. Those that "live" are very unhealthy and will not live as long as a life as usual. So those that think that if they use a fish to cycle a tank and the fish live...those fish are pretty much dead already and will live a very shortened life, that is if they didn't die during the process of cycling the tank.
To use a fishless cycling it's cycled faster, no fish are harmed and you can add ALL the fish you want to keep at once and it's ok.
If you cycle WITH fish, you shorten the life expectancy of any fish you choose to to cycle with, IF they live, you can't add more than 1 or 2 fish after the cycling is done, to let the bacteria build up to handle more of a bioload of fish and even then, the fish you already have established suffer in the process.
Fishless cycling is the only way to go if you love fish.
