This is a question that every hobbyist asks when they are first building their aquarium. Most people in the industry will tell you that you need your tank to turn a certain number of times an hour. This number varies but ten seems to be the most popular answer. The problem with this answer is that it does not actually address the question. You see in a reef aquarium not only flow but intensity must be considered while designing a system. a 100 gallon aquarium with twenty 50 gallon per hour pumps will not work. It would stagnate and keeping corals alive would be a challenge. A 300 gallon aquarium could not have a single pump and single one inch outlet at 3000 gallons per hour, as coral tissue would be torn off of the skeletal structure.
Flow and intensity can not be accurately predicted as you build the aquarium, as the needs will change as the tank matures. Just make sure you build a aquarium that easily allows you to modify the flow and intensity.
Tips:
-Don’t plan on your first pump being your last one. A healthy aquarium will require more flow as it matures so you will need to change pumps over time.
- Don’t use your return pump as a circulation pump. Use it to move your water through the sump but keep the flow accurate. A return pump should should move the sump water back to the aquarium not to exceed 20 times per hour. If the sump is a refugium it should be slower.
- Understand the difference between flow and intensity. You can have great intensity pushing 50 gallons per hour out of a 1/2″ pipe than 500 gallons per hour through a 2″ pipe. Most SPS need lots of flow but intensity will hurt them.
- Always use the manufactures recommended plumbing size for pumps.
- Understand that the intensity drops by 2/3 with every additional return you plumb at the same size as the original (using the manufactures recommended plumbing size)