Here can be a step by step approach if you NEED more PAR. You probably do not. 300 near the bottom and 400+ up top is pretty solid... those can probably get to 325 and 450 if you lower it a bit.
1). Lower the fixture
2). Remove the glass from the fixture - you have to clean the bulbs and reflectors more, but this is a lot more output. Don't do this with DE bulbs, just SE.
3). Go to lower K bulbs - 14k or 10k and make up the color difference with T5s
4). Buy m80 ballasts and drop more wattage in there
5). Go with 400w gear
I don't think that you will need any of this, but this what you CAN do if you have to.
FWIW, 20k Radium on m80 without glass puts about 800 par at the top of my rocks also in a 27" deep tank. These are 80 more watts than regular 250w ballasts, though. I am at about 400 in the lowest depths. I did this on purpose to get faster growth, but it is certainly no necessary.
1). Lower the fixture
2). Remove the glass from the fixture - you have to clean the bulbs and reflectors more, but this is a lot more output. Don't do this with DE bulbs, just SE.
3). Go to lower K bulbs - 14k or 10k and make up the color difference with T5s
4). Buy m80 ballasts and drop more wattage in there
5). Go with 400w gear
I don't think that you will need any of this, but this what you CAN do if you have to.
FWIW, 20k Radium on m80 without glass puts about 800 par at the top of my rocks also in a 27" deep tank. These are 80 more watts than regular 250w ballasts, though. I am at about 400 in the lowest depths. I did this on purpose to get faster growth, but it is certainly no necessary.
