You might be able to rent a diatom filter at your LFS. I know my local "mom and pop" store have one for rental.
I would do very frequent water changes. I had the same problem in my tanks after setting them up with a sand substrate. I rinsed and rinsed and rinsed the sand prior to putting it in the tank, but a month later the water still had a brownish tinge. Do some large and frequent water changes, and place a saucer or plate or something on the bottom of the tank when replacing water so it doesn't stir the sand up more when the water hits it.
I don't think a powerhead is going to help your filtration out all that much, however they are really good at moving water in "dead" spots around so everything circulates itself to the filter path.
I would do very frequent water changes. I had the same problem in my tanks after setting them up with a sand substrate. I rinsed and rinsed and rinsed the sand prior to putting it in the tank, but a month later the water still had a brownish tinge. Do some large and frequent water changes, and place a saucer or plate or something on the bottom of the tank when replacing water so it doesn't stir the sand up more when the water hits it.
I don't think a powerhead is going to help your filtration out all that much, however they are really good at moving water in "dead" spots around so everything circulates itself to the filter path.