Question about adding clowns

[Aquatic Pet]

About a 5-6 weeks ago, one of my Ocellaris clowns disappeared. I literally looked everywhere and came to the conclussion that he must of passed and got sucked up in the filter. I have checked all my levels and everything is perfect, no issues with any other fish, inverts or corals.

My kids really liked the clowns and my other clown now seems lost without his little buddy. Do you think it would be ok if i added another occellaris clown so i have another pair? Also, if i can, should i go smaller or bigger then the one i have in the tank now?

The tank is 55gal and i have 1 ocellarus clown, 1 royal grama, 1 yellow watchman goby and a bunch of crabs, snails and inverts.

 

[little_fish]

I would add another clown, just add one that is either much bigger or much smaller than the clown you currently have to cut down on fighting