We received the replacement sealing gasket for our aquarium filter today. We installed it into the filter, and hooray! the filter doesn't leak anymore!! Neither my DH nor I were completely convinced that this would fix the problem, but it did. We also bought 7 fish for the aquarium on Monday - 3 gold twinbar platys, 3 cherry barbs, and 1 red velvet swordtail. I'm looking forward to getting a lot more fish, but it takes about 6 weeks for a filter to operate at maximum efficiency, so I guess I'll just have to be patient (never my strong suit!).