They are sometimes kept with agressive African cichlids. Reason being is they have an eye tooth srt of a bone below the eye. This is razor sharp and though they are not agressive when agressive mbuna (an african cichlid species) mess with them they will turn their head and give the African a nice jolt. The Africans learn to stay clear of them. Big central or south american cichlids if larger would kill a clown loach though. They are suseptable to ich and have no scales so I would keep this in mind in regards to water quality. Hope this helps a bit. Three is fine together.