Hi I got 3 tetras ( TETRA SERPAE) just two days and put them in 10G new tank. For one day they were fine... and i fed them couple of tropical flakes( did not over fed) . Now they are not eating .... they have no energy left one fish is already on the ground .. but looks like breathing .. one fish is at top of the tank and another is in middle of the tank.. I have no clue what to do ... its just second day .... and do I need to change the water.... please help