you can absoulutly ATTEMPT a shrimp in the tank infact im willing to bet your harlequin is encoureging a live shrimp in his tank
trigger wouldnt mind a shrimp either ***) ***)
notice I empahasised attempt
with my expirence my halequin wouldnt let a shrimp out of his sight
and triggers are the same way
but if you are going to try one
while acclimating the shrimp feed your halequin and trigger and till they refuse to even look at food
then maby they might get along
and make sure you keep your harlequin and trigger well fed