What type of powerheads do you have? If they were used on a UGF they may be set up to run in "reverse flow" mode, they may need cleaned, or they may not have a good flow rate to begin with...it's hard to give any better info without knowing the brand you have.
As far as the "seeded" filter, has it been running on a tank with fish in it? If it has been sitting on a tank without fish, it probably isn't "seeded" any more. The bacteria need a food source to stay alive, i.e. ammonia from the fish.
As far as the "seeded" filter, has it been running on a tank with fish in it? If it has been sitting on a tank without fish, it probably isn't "seeded" any more. The bacteria need a food source to stay alive, i.e. ammonia from the fish.