I have just recently set up a new tank ,and recently placed two pregnant female swordtails in it whilst i think what i want to put in it permanetly ,these are the only inhabitants. They have been in it for about three days and apart from one female chasing theother they seemed to be settling down except last night I fed them a bit of frozen brine shrimp within seconds of it hitting the water they seemed in a highly stressed state and started darting about with fins fully extended,Today I went to feed them some flake food and again they went beserk.Im not banging the lid or doing anything to suddenly scare them,the day before all this started i fed them some daphnia and they seemed ok,could it be they have smelled the fish and as they are the only two in the tank (they were in a big community tank before) they are scared?