10-30-2012, 03:21 PM
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Under gravel filters (UGF) can still be effective bio-filtration but require routine, if not religious, gravel vacuuming to prevent fouling. In some respects, reverse flow UGF's are better. In some respects, as Taz points out, UGF's are 'old school' in favor of todays power filters and medias. AND if rooted plants are in the short/long range plan, a UGF would be best avoided.
As a matter of fact, having used both gravel and sand, I'm sold on sand and would use sand instead of gravel.