I have a tub outside my balcony which I grow my water lilies. I put an UGF folowed by pebbles followed by water lily clay that you can find in the botanic shops. Is it the correct way to apply lily clay? I wonder if the clay itself is like soil (it cannot be exposed or it will leach chemicals?)

The reason I ask is because I tried putting guppies, mollies and swordtails into the pot and the only fish that can survive are the guppies. My swordtails go haywire in their ability to swim after awhile then they die. My baby mollies magically dissapear (bird ate them?)

I have cycled the pot for at least 3 weeks before introducing the fish. I tested the water for ammonia and the reading is very low (0.1?????). Makes me wonder if the clay is the culprit for the fish's death. In which case, must I cover the clay with a layer of holland sand?