When using a wooden hood it is always best to try and reflect as much light back into the water as possible from the tubes. This is usually done with aquarium reflectors which can be quite expensive especially on larger hoods.
A cheaper alternative is to use tinfoil and wood glue. I have used this technique on all of my wooden hoods and it works a treat. Cover the inside of the hood with wood glue then carefully lay down the tinfoil and smooth flat. Try and wipe of any access glue before it dries and don`t worry if you rip the tinfoil because you can easily patch it up. If the hood is quite large then you can always do this in sections to make it easier as the tinfoil may get a bit sticky.