Firstly I need to know if the tank is the 30 litre? Is it cycled? what filter is in the tank? what are you current levels, ammonia, nitrite, nitrate etc?
Just read your earlier post, you would be better to acclimatise longer especially with the likes of fragile fish, float the bag for 10 mins, then add a small amount of water and repeat every 15mins for an hour. It also sounds like an ammonia spike probably because the tank isn't cycled yet.
Every time someone asks me can i put Clown Loaches into a 10 gallon tank, a little piece of me dies.