"I used the reverse flow, pumping water into the under gravel, bring more oxygen under the gravel, drive the waste out from the bottom, which will catch from the regular filter. Yes, you will need to clean the filter regularly, but it is better than sucking all the waste into the bottom of the tank and leave it there. I believe my fish is healthier and happier. One catch, beware of baby fish and small fish, it will suck them into the under gravel as well. "