Engineer goby Reef safe or murderer.

So i need to replace my sand sifter in my tank. RIP cookies (diamond back).

I looked into engineering gobies and they seem like a good match for my tank. Then i did a little more research and i heard a couple stories of them killing fish and inverts. Live aquaria says reef safe and peaceful. Which one is it reef safe peaceful little worker, or mass murderer waiting to grow big enough to run the tank.