dither fish

Do shell dwelling multis need dither fish to feel comfortable? I want to make sure they are as happy as possible, and they seem SUPER nervous. I did get more shells, 18 of them in the tank now, and each of the three fish seem to have picked out their favorites. The tank is a 30 gallon and 30...

Is this okay? I don't know if it will cause stress or if it is just a good outlit for aggression. I don't have any dither fish yet so I didn't know if it would be a good distraction for them or not.

Ok iv spent all morning travelling a hour and some to get some fish , I buy 8 Columbian tetra and 5 silver dollars I return home with in 10 minutes I have 3 tetra and 1 silver dollar , my Oscar is a complete penis and it’s really annoyed me that I have gone out my way to buy dither fish suited...