Hi,
9W led bulb's can eat a lot!
I would dismantle the bulb and put some new termal paste.
I would bet in 3W and 4W led bulb's (6500ºK) with good lens on it.
I use 2 cheap bulb's like these:
http://www.miniinthebox.com/pt/gu10...tual-220v_p831302.html?utm_campaign=cartcross
And they are very powerful and very decent depth penetration! [check CovaMoura]
You can safely put your hand in any bulb at the end of day! (this is one of my criteria for choosing bulbs)
I also (very cheap 3W) have 2 like this:
http://www.miniinthebox.com/pt/gu10...-led-light-bulb-pontual-220-240v_p723099.html
But they don't have lens. Even without the difuser the light power is miserable! (I can measure in lux's if you want, sorry but no PAR meter!)
The colour led's can be inside water? did you try with the light fixture?
One more opinion, (sorry!) i used also the metallic fixtures for the bulbs but they were a little bit disturbing (for watching and photos).
Maybe more 5 -10 cm of black wood...
I have redone my light system a few times an still have some issues to deal! (but this is also the funny part of the hobby)
Thanks for sharing your project,
cheers
tiago