[/IMG] Heres a quick pic of my six juvenile rbp's, I have had these two months and they were two-three inches when I picked them up now they are 5-6 with one runt thats still 4 inches, they are in a 40 UK gallon and now need to go up to a 100 UK gallon. Will post better pics when I put them in the new bigger tank.
Regards Jon
That depends on many factors, how big they were to start with, how much you feed them, the footprint of the 47 gallon tank and who you talk to.
This is just my personal experience though and others may recomend otherwise.
I will stick my neck out and say, Starting with babies as small as you can get 6 months maybe more but you will see a change in the behaviour they get aggressive towards one and other and may eat each other, When I first started I kept five in a 48"x15"x12" for years but ended up with one large one that was the badest piranha Ive ever owned . That was years ago and before the internet and all this infomation that now exists.
Ideally allow 20 gallons each fish if you reduced to 3 you would be able to keep them in the 47 gallon longer because after a year or so their growth rate slows down.