How High Should the Suction Be With Aquarium Filters?

You have many options for aquarium filters, most of which are rated by how much water the filter can cycle in an hour. Different types of aquarium filters have varying guidelines for how much water they can filter. Regardless of how they're listed, most of these guidelines will equate to the volume of water they can filter per hour.

  1. Filter Ratings

    • Most aquarium filters are rated in GPH. GPH stands for gallons per hour, the volume of water a filter can cycle through itself in one hour. Most modern aquarium filters, including power box and canister filters, have GPH ratings. However, many DIY aquarium filters are powered by external water pumps. Such filters are usually measured by their pumps, which are similarly rated by GPH. For this reason, most guidelines on selecting a filter are based around the filter's GPH.

    Powered Filters

    • Most modern plug-and-play aquarium filters fall into the powered filter category of aquarium pumps. They include filters like the powerbox or hang-on filter and the canister filter. These filters feature internal pumps that suck in water from the main aquarium and push it through the filters. You typically want a filter rated to filter 6 times of volume of the aquarium per hour. For example, for a 10-gallon aquarium, you want a filter rated at 60 GPH.

    Sump Filters

    • Sump filters feature prominently in the marine aquarium. Many hobbyists make their own sump filters rather than purchase them. A sump filter consists of a separate container of water filled with biological filter media and aquarium equipment, and a pump that returns water from the sump to the aquarium. Depending on the height difference between the sump and the main aquarium, a pump's GPH rating will vary. However, most pumps come with charts that show different GPH ratings based on how far they have to pump the water. For a sump filter, you want a pump rated at 3 to 5 times the aquarium volume per hour at the height difference between your sump and the main aquarium.

    Protein Skimmers

    • Protein skimmers work better in saltwater than freshwater; many hobbyists consider them critical for marine aquariums. In protein filters, tiny air bubbles are pumped through the water column. These bubbles attract organic wastes and bring them to the water's surface in a fine foam. Unlike other filters, protein skimmers function best when the water moves through them very slowly. Your protein skimmer's pump should be rated to cycle only two times the aquarium's volume per day to ensure the water has enough contact time with the bubbles.