Premium Member
Are there any smaller mantis shrimp(6inches or less)that are really colorful?I am looking for one to put in my 10gal and have heard a peacock will grow tp large.
It is rare that any peacock survives long enough to grow much in captivity. Even if you have one a couple of years (a reasonable time to expect to keep one), they are not likely to grow more than two or three centimeters. I would not let concern for the animal outgrowing your tank keep you from acquiring one.

That said, there are lots of really colorful gonodactylids and odontodactylids that do very well in a small tank. Colorful species that I would recommend include Gondactylus smithii, Gonodactylaceus ternatensis, Gonodactylus platysoma, Odontodactylus brevirostris, Odontodactylus havanensis, and Haptosquilla stoliurus. All are colorful, tough, and I have seen all of them occasionally available from wholesalers. Pseudosquilla ciliata can also be very colorful and makes a good aquarium animal. If you want something really exotic, try for an Echinosquilla guerini, a red and white species from the Pacific that mimics a sea urchin.