Ok do Severums have to be in groups. And what size should the bichirs be before I put a severum in? Will severums attack plants? And for the Oscar, will they attack plants? What kind of severums would you recommend?
I've tried this fish in groups be it two of the same gender all the up to a group of five of the same gender. They always fought, and this was in a 300 gallon. If you try a male/female pair, if they pair up romantically, they will take over your entire 75 gallon tank and kill their tankmates when spawning. They become hyper-aggressive during these periods.
I would get one severum with your bichirs. If you want to add another fish with your severum, you could try a leopard ctenopoma. They are peaceful as long as you buy them small and grow them up on flakes, pellets, and frozen. Feeders will increase their aggression in the ctenopoma. If you'd rather get something different than a ctenopoma, a black ghost knifefish also works with severums and senegal bichirs if you get the knife larger than the bichirs. Be sure to keep the bichirs well fed, and never give them feeders so they don't nip at your knife. If you want to add motion in the tank, you could add a dozen congo tetras or a group of roseline sharks for mid-dwelling fish, and maybe five to six yo-yo loaches or polka-dot loaches.
As for your other questions, it doesn't matter when you put the severum with the bichirs. You can put them in at the same time or one then the other. Any severum subspecies will work, so do an internet search on the different variants of severums, see how they look when they are adults (they color up as they grow), and choose the one you prefer.
