Is it cycled? How new is the tank?
Are you checking for water parameter issues?
Did you use live sand or LR
What kind of maintenance schedule are you using?
New to FW fish? First tank in a long time or EVER??? Need some info on keeping fish?
Start here - Aquarium Advice Article
FW Favorites right now Clown Loaches, any shrimp - SW Vase Red Mangroves