Hujeta characins are nice and never leave the surface except to feed. Or maybe pink tailed chaleus's. The hujeta's eat mostly feeder fish thou so that may be a problem if the other fish are very small. But if they live with bichirs and eels they should be OK.
Out of interest, how are the tiger loaches faring with the other bottom dwellers? What species do you have? Any pics? What species are your synos and bichirs? Your tank is ridiculously overcrowded with bottom dwellers. How big are all these fish?
i have 6 tiger loaches and they love my two large pieces of drift wood they are no bigger then 3 inches, for the bichirs, i have an ornate that is about 8" delhezi which is about 4" and 3 senegalus with range from 3"-6" i have two 7" unknow to me synodontis in which i maybe wrong, the cats are not on the bottom either but i will post pics of what i have