dzeadow, I have never kept any shrimp gobies without a pistol shrimp, so I'd imagine that you don't see yours because they're missing their hole digger, and perhaps they don't feel very safe without a proper hole. I'd definetly get them a shrimp. You said you've got a couple of hi-fin bandeds, and I've personally seen mine share holes in different ways - I've seen them with 2 gobies per 1 shrimp, 1 goby per 1 shrimp, and 1 goby per 2 shrimps. If I were you, I'd try for 2 shrimps seeing as the way they pair up is completely up to them (2 randalli or 2 tiger pistols - not one of each). If you're worried about noise - I must say I've not heard mine click EVER. I keep five randallis in this tank and have not heard a single noise to date. I have only kept one tiger pistol before with a yellow watchman in another system, and I never heard a sound from him either. I imagine it is a defense feature, and since I have never kept any predators to these shrimp, there's been no need for them to "shoot". Hope this helps - let me know what you end up doing... :]