It is fairly common for various species of clowns to accept a substitute to a nem.
My picasso's for example took host from hammers, frogspawn, even a monti cap before they finally accepted my Malu.
The only negative reaction I had was the monti cap, as they started to groom the area to spawn(it's finally coming back from what I thought was completely dead)
My hammer and frog never showed any neg signs at all.
The benefit of this type of substitute is they don't wander like many host nems can.
I actually prefer this type of setup in small tanks.