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How to Determine the Filter Flow in an Aquarium

When you purchase a new or used filter for any aquarium it is important to decide whether it has an appropriate flow rate for the size of the tank it is to be used on. Although it is easy to do, the calculations use rather large multiplication numbers. In addition, the flow rate is an irrelevant number, even though it is placed on all filters, without doing the final calculation to see if it will turn over the water in the tank enough. The rate of turnover should be five to 10 times. For example, a 20 gallon an hour flow rate is great for a four gallon tank but not a 10 gallon one.

Instructions

- 1
  Locate where the water touches the glass at the top of the water and where the top of the sand ends. Measure and record the distance between the two. Measure and record the length and width of the glass.
- 2
  Multiply the length times the width. Take the answer and multiply it by the distance between the top of the sand and the top of the water. Divide this answer by 231.25 to get the gallons in the tank. If you are not a math whiz or cannot find a calculator, use the calculator at Aquaticsbydesign.com. Record this answer for later.
- 3
  Turn the filter off. Attach a 12 inch plastic hose to the port that expels the filtered water. Get a clean one gallon container and direct the hose to spray into the container. Turn on the filter and time how long it takes to fill up the gallon container.
- 4
  Turn the filter off. Divide 60 by the time it took. Multiply the answer by 60. You now have the flow rate in gallons per hour. This is the rating that the manufacturers use. Remove the tube and turn the filter back on.
- 5
  Divide the answer from step two, the total gallons of water in the tank, into the flow rate from step four. This will tell the turnover rate per hour. This should be between five and ten, with the higher rate being better.

Nature