"OK, let's get one thing straight. If you bought this for turtles, take it back now and get something else, like a ZooMed. These filters really aren't designed to manage the volume of waste turtles produce.
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If you bought it for your aquarium, these little filters are surprisingly effective. Yes, the plastic case can be brittle, so be sure to handle it carefully, especially when renewing the filters. (BTW, sponge filters can be reused if they're not overly clogged, and if you're enterprising, you might be able to disassemble the plastic carbon containers and refill them to save money. I do.) If there's alot of crud in your aquarium, the intakes are small, so they're easily blocked. If the pressure drops, check the impeller assembly for clogs/tangles; be sure it spins freely.
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Bottom line: It's compact, it's internal, it offers filtration and aeration options (which many in its price range don't) and it's actually pretty inexpensive. Don't overload it (turtles, goldfish) and be sure to maintain it, and it'll do what it's designed to do."