Review on Penn-Plax Undergravel Aquarium Filter for 10 Gallon Tanks - Enhance Water Clarity & Purity - Freshwater/Saltwater Safe - Two 9.5” x 9.5” Plates by Erica Rogers

Suitable for filtration, excellent for aeration. I found the hoses to be too big for a standard 10 gallon tank so I had to cut them or the water level would be too high - had to fill them to the brim to aerate and then the filter wouldn't work. it works correctly. Don't put too much gravel on it or it won't soak up food. It's also quite difficult to remove the tabs from the bottom to hook them. The lower part fits perfectly into the ground. The picture above shows the gravel before I carved half of it. (Ignore the arrow!)