Its up to yourself if you want to seperate them, if you have a spare tank i would. By the way you need a bigger tank, i wouldnt keep that ornate much longer in the 20, you need to upgrade to a 75-125 soon.
Wow man i cant wait until my ornate gets that big, right now he is a small fry only about 3inch big, how long did he take to reach 9". I am feeding my ornate krill will that make him grow fast. I have some pictures of him on the where to find delhezi in nyc post. (oh sorry didnt mean to highjack ur thread either
I traded in a wolf fish and tiger oscar for the ornate cause the wolf fish kept jumping out and the oscar was a pig plus i wanted a bichir tank i got him at around 8'' so i haven't had him more then a month or 2.
I wouldnt risk it at that size differences,my 12" endli tried to eat a fat 7" endli after being in the same 180g for about an hour so i dont risk it anymore,and the ornate will keep growing so i doubt that the del would catch up until the ornate reaches a size when it slows down considerably but then the size difference will be considerable too,ive got a del and it doesnt get bothered by my others but he is a decent size.
i wouldn't worry about it. i have done these kinds of combos a million times without anything tragic happening, though it still depends on fish personality but the statistics shows.