Parts on the year clown loaches spend in soft black water habitats, so to me cichlids that inhabit similar waters would be my choice. South American cichlids from Amazonia east of the Andes, or west Africa would fit that bill, and the South Americans from those habitats tend to be a little less aggressive.
And as said above, cichlids being substrate huggers and territorial as are substrate loving loaches, so choosing mid water, or small to medium cichlids might prevent conflict.
Geographically speaking, clowns being from Borneo and other parts of South East Asia where no endemic cichlids are found, so I would think gouramis, or wild type Bettas would be a more correct choice. And since clowns tend to appreciate fast moving water, some of the wild mouth breeding Bettas found in fast moving streams in Borneo, would be perfect.
And example, Betta albimarginatta

These Bettas are able to be kept, in groups (,ales and females) and I used leaf litter to supply tannins, that the clowns might appreciate for their anti-bacterial health reasons.
