Hi,
HAve 3 Tunze and 2 nems, my malu does alot of walking around but never to near the tunze as the blast from them i think to so great the nem does'nt go too close, had them a few years now and the malu gets close and then move away when it start to fill the current.
Also the tunze have the inlets on one half of the cover and I always have the grills on the upside of towards the glass to stop bits getting in.
As for my malu it's huge and eats but likes walking.