I don't think you will get away with haveing any slow tankmates with your fahaka. I tryed putting a 13in gar in with my 6in mbu and and he did some nasty damage to it. You would be suprised what they can do. If he goes after your RD he may do some fatal damage.
The only thing I have been able to keep with my mbu is fast swimming tetras, and he still catches them on occasion.
The only thing I have been able to keep with my mbu is fast swimming tetras, and he still catches them on occasion.