Best Aquarium Filters of 2025: Top 6 Picks for Every Tank Size
The filter is the most important piece of equipment on your aquarium. A good heater keeps the water warm. A good light grows plants. But the filter is what keeps fish alive. Without adequate biological filtration, ammonia builds up, fish get stressed, and you end up with sick or dead fish no matter how careful you are with feeding and water changes. We tested 6 aquarium filters across three main types — hang-on-back (HOB), canister, and sponge — in tanks ranging from 5 to 75 gallons. We ran each filter for at least 4 weeks, measured flow rates, noise levels, ease of cleaning, and how well each one maintained ammonia and nitrite at zero in a stocked tank. ...