All the lysmata sp. shrimps are kinda shy. I keep 2 species, the skunk cleaner (L. amboinensis) and peppermint (L. wurdemanni) The pepps stay hidden much of the time only comming out much at night......the skunks hang out at the bottom of large rocks - just above the gravel, but visible during lights on. But during lights off, they too can be found roaming everywhere.....
Your species - Lysmata debelius is gonna be more active during lights off and probably rarely ever seen during lights on. Take a dim flashlight and search for him a couple hours after lights off - you'll probably find him out & about searching for food.... I'd NOT expect to see him out much during lights on - Unless you have a fishless system, in which case within a couple months, once the shrimp realizes he's not gonna become food - then he may spend much time out during day-cycle. Additional shrimps of the lysmata sp. won't really help, i've 6-8 peppermint shrimps in my main, and only ever see them much at nite, and 3 skunk cleaners all hang out together - but again, they hide somewhat too.
