I see that you put the similis in your established 75G calvus and petricola
Would you share what are the effects adding new shellie in an established tank like this?
I mean the similis are the smallest between those three species, aren't they harrased by the others?
No not at all. Calvus are fry predators and same with petricola. These are adult or juvenile similis.
I prepared the shell bed and I released the similis directly over the shells. Initially they claimed a shell or lurked at the edges of the shells.
Today much the same but some are over at the calvus rock pile and the calvus are ignoring them.
If anything I see one much larger similis and so maybe I need to spread out the shells more in case he is chasing other males away from the six inches he has claimed.
IME if you add several new fish at once, especially if they are not a species that competes with the species already in the tank, you are fine to add juveniles or adults to an existing tank. Relative size of the fish is not a factor, as long as none are fry.
In the past I have also added juvenile calvus to a tank with mature calvus. Also fine. Just don't add one or two, and don't add fry that are too tiny.
Thanks. Definitely similis are fine with calvus and synodontis. But the 2 smallest similis...one is chasing the smallest one to the surface. I will have to make changes to fix that. The joy of cichlids!!