i have balanced the plane right on CG point

the instruction says balance with no fuel in the tank but every thing else.

and i found that my fuel tank is just infront of the CG point but close (wing tube is at the back of the tank)

if after fuel up the tank, the plane will be nose heavy, do i need to balance it again or leave it ?

Thanks.

Balance it empty
It will be somewhat noseheavy and more stable when filled,and will slightly change as you fly.Usually its not very noticable.
On very high performance aircraft we try to get the tank right on the CG ,so there is no trim change during the flight.
On trainers and most sport aerobats its a non issue.You'll be fine

Ok got it !

thank you