The bichir may go after the angel's fins, whether or not the fish's body will fit into its mouth. Also bichirs can be kinda stupid about food, going more by smell than sight, so the pictus may outcompete it. They can also be somewhat picky, and are known escape artists, so a tight fitting cover is a must. My older bichir will eat anything, but the new one that was dropped off at work went on a hunger strike for a few days, even tho it was obviously underfed when it was brought in. I finally got him interested in food after I dropped a piece of beef heart on his nose, but he's still a picky eater. The ever hungry sunfish usually ends up eating everything I try to feed this bichir.
The eating habits between the 2 bichirs are interesting. My older one is a very active fish, and readily eats right along with the other fish in the tank. The newer one "plays" with food before actually eating. It will grab a piece, mouth it, spit it back out, and then repeat the process a few times before deciding to actually eat. This usually gets the attention of the sunfish, who will swoop in and grab the food when the bichir spits it out. The tank is 6 feet long, so I feed at opposite ends to distract the sunfish, and I've even used the planting tool to place food right in front of the bichir.
Based off the personality of my older one, I'd say go for it because they are very interesting fish.
