>> Can someone suggest a form of filtration that would suit the tank, and leave
the water and the gravel clear of dirt and debris?? <<
While not exactly filtration, I do have a suggestion. Purchase a small
powerhead, a 170 gph or even the next size down. Fix it so that the output is
about 6 inches above the gravel and directed straight across the top of the
plants. While it itself will not filter anything it will keep debris and dirt
suspended until the canister filter gets the chance to get it out of the water.
To increase efficiency get on of the filters that comes with the coarse
spongelike prefilter. This will also help keep mulm from forming.