you cant go by someone elses growth rate. if you dont have the room at the time or plan on getting it sooner rather than later, then i wouldnt get it. depending on the diet of the fish, water parameters etc, it could grow quicker or slower. i dont own a fahaka(i have GSP and Figure 8's) but all of the FW fish i have kept have grown anywhere from only an inch to 5 inches in a matter of a few months. wait til you have the tank he will be in permanently, save yourself the hassle and save the fish the stress of moving. find something to occupy the 60 and keep you happy while you wait to get your big tank for the fahaka. just my own opinion, do as you please