Here has been my experience, hope it helps...
I had a pair of ocellaris for years in a 28g. These guys were hosting a kenya tree and laying eggs. I moved them to my 210g when it was finally ready and they took over the entire tank. I mean no other fish allowed period. I had to re-home them.
More currently. I had a pair of ocellaris (snowflake and mocha) that had been hosted by a large bta and happily laying eggs regularly. I later added a pair of baby blackfoots (A.Nigripes). Everyone was fine for a few years. The nigripes found a nem in the center of the tank and the ocels were on the far right (I have a 7' tank). Now, I had a nice pair of clarkiis that I added with their own nem to the left side of the tank. Within a week, I had to catch them out because the nigripes were killing them. They now live in my sump (nice large area). Well, eventually the blackfoots aged enough and began laying eggs too. All was well for another year. Then, boom, one day the female nigripe decides she wants the ocel nems too.
Killed the female (I was out of town when happened so could not get out in time), but babysitter managed to get male out before death and he is in the sump. So, now I have a pair of nigripes that are in a 210g (only clowns, but lots of other fish introduced and they are fine), clarkiis in the large area of the sump, percs in my 40g, and one lonely snowflake in my smaller sump area.
Moral of the story is clowns can be fine one minute and decide to kill the next. I may try to introduce the clarkiis again since they are soo large compared to nigripes, but not until have a nice hosting nem first.
In that size tank I would only do a pair. Especially since you are newer. Good luck!
