your best bet is to try and get them at the same time and acclimate them together like I did... they found eachother right away. If not, you can get the Aurora and put it in, make sure you watch where it calls home. When you get your pistol, after acclimation, put it in a net and hold the net closed until you get it towards the goby's hole and leave the net there. The pistol will have a better shot of finding the goby and vise versa. As for the gobies fighting.. not sure. I've never had an engineer goby so I don't now how agressive they are.