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 Kathleen Herrera

So easy to use! I use this with small river rocks - a bag from the hardware store. Rinse the stones well before use and place them on the grate. The aquarium has a stable pH, contains rock minerals, has no sharp edges that can injure fish, and requires little maintenance. Maintenance costs are minimal. The cheapest, best aquarium system on the market and the most natural! I've been using it for years and can't be happier. Weekly water changes and carbon filter changes are a breeze and require a lot less work than other systems. A tip for the activated charcoal filter: buy activated charcoal loose and fill your own filter - even cheaper and easier.