Should be noted that this is a brackish species. Been keeping a pair of these in a 75G eel/puffer/molly/rainbow setup for about 2 years at an SG of .09 - .13 @ 80F.
For such a strange collection, with other oddballs mixed in, they are very tolerant in temperament of others and each other. They can be big eaters. and will learn to take almost anything; frozen bloodworm, mysis, squid, daphnia, live shrimp or worms, and even certain flakes. As long as they have a crevice or cave to hang out in, they'll stay happy.
A female can be identified by her somewhat smaller fins and having a yellowish cast to her body or dorsal, whereas the male will have more of a brilliant blue about his iridescence.
I have 4 knight gobies in a slightly brackish tank (extremely hard water). I've had both pairs spawn several times, but I have not had any success raising the fry. The fry are extremely tiny and would need rotifers or something smaller to eat. They spawn every 30 days, and I always do a water change on the 29th day. The coloration of these fish changes quite a bit during matiing as their fins will outline black and the normally black areas will be clear (have only seen this twice ever). My fish only spawned when the temp was 74-77 F (I know, it's odd). These fish will eat anything that will fit in their mouth, so be careful what fish you add to their tank. They seem to get along with any fish they can't eat, but I have not put any aggressive fish in their tank. A sand substrate will allow them to demonstrate their aptitude towards digging.
I have had my night goby for 2 years now and he does great I have three green spotted puffers , three silver monos , 4 green scats 3 golden wonder killis and a couple of sailfin mollies all o the fish get along great and have for the last couple years it should be noted that none of these fish are more than half there full grown size and from what I hear my puffers may eventually eat everything
Beautiful fish with a very interesting personality. Except that, I had to move it out of the community tank as when I put cardinal tetras in, he immediately went after them with serious intent to eat them. Must say, he is doing really well in non-brackish water.