Hi, I suspect i am probably too heavy handed - they go mad when the
feed comes in (once a day - a small pinch), but i only have 4 pencil
fish, 4 guppies, 2 harlequin tetras and 1 neon, so perhaps not
overstocked for a 50litre tank?

thanks

How's your hand at feeding? Light or heavy? Does any food reach the
substrate?

What is your tank size and fish load? Are you overstocked, and making more
waste than your tank can allow?