Freshwater nocturnal fish.?

Hi, I have a cycled 120 gallon tank. i now have 1 Discus after a sudden disease truck I had 8 before 26 neon tetras 20 wihte cloud minnows 2 corey cats and 10 glcatfish. I'm looking a pleasent nocturnal freshwater fish. to add to my aquarium. I was thinking clown loachs but those get awefully big.