Recently I got four killifish, I'm positive one is a male but I'm not sure about the other three but anyways, They haven't been exploring the tank at all. They have been sitting at the top of the tank for the past week. My tank is 75 gallons and stocked with zebra danios and dojo loaches. The ph is fine and the temp is as well. They eat fine but they just do nothing other then swim at the top of the water.