Ok on the week end I swapped most of my gravel to sand and purchased 5 peppered corys feeling bad for them because they were hiding I buy another 2 and put them in , it worked and the others came out and joined up with them , Problem the first 5 were around 3cm the second 2 were smaller around 1-2 cm I did a reshuffle on my tank last night and while the tank was empty I noticed only 6 corys with the smallest gone not even a body , can’t decide who would of killed it , geophagus? Electric blue acara? Colombian tetra? Or pleco , in fairness it was that small my pleco probably wouldn’t notice eating it but for some reason I have a hunch it was the tetra sounds daft but they do bunch in a 8 a they are bigger than the Cory was so possible they stressed and killed ?