Glad we got that cleared up
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Here are a few quotes from the first page of google about knight gobies:
"Anyway, my problem is, he keeps eating the majority of his tank mates. He seems to enjoy the company of the clown loaches, but he's eaten all my neon tetras, danios and all but one white cloud. The rasboras and the clown pleco are apparently too big for him to eat, so he doesn't bother them much. He even ate the fins off a sailfin molly, and eventually killed it. No one around here will take the goby, not that I really want to get rid of him anyway, because he is very beautiful. What other fish can I put in with him?"
http://www.wetwebmedia.com/brackishsubwebindex/knightgobyfaqs.htm
"Territorial by nature, the aquarium should have plenty of places to to hide such as caves, driftwood and plants. They will defend their space......While not an active predator, the knight goby will eat smaller fish in the aquarium, being shy you would not want to keep them with overly aggressive species like the larger cichlids"
http://badmanstropicalfish.com/profiles/profile98.html
Also, the caresheets alter from "They do best in freshwater!" to "they do best in BW!". Probably they do best in low-end brackish. Again, the brackish people would know better than I, lol.