I have built a LED fixture for a standard 10G tank (20 L x 10 W x 12 H). I used 3 watt Crees - 6 blue and 6 white, using 2 buckpucks and external pots for dimming.

I have two questions.

1) - I used the pots recommended on the data sheet for the pots - and frankly less than a 1/4 turn is required to go between min an max on the brightness. Will a different pot help? Recommendations on what to try?

2) This thing is bright. Given that it is less than 12 inches to the sand I worry that it may be too intense. Does anyone have experience with a similar arrangement? should I run these significantly dimmed? I think it will blind the fish ...