A Zoo should keept the safty of its animals as the most importent factor. It is just a foolsih idea to fill it with an species, which only because of that single reason don't fit. While there are so many hebervious,insectovor and piscivore options exist, that are aviable. Like I said, in my opnion would the black and rufous elephant shrew, (maby together with an african tortoise species) be a perfect fit. It is a decently sized animals, active at day, coudn't escape, and is alllready succefull kept together with smal birds, with no problems.