How big a pump do you need for 40 gallon tank with ten sump?

The size of the pump you need for a 40 gallon tank with a sump depends on a number of factors, including the size of the sump, the desired flow rate, and the head height (the vertical distance between the water level in the tank and the outlet of the pump).

A general rule of thumb is to select a pump that can provide a flow rate of at least 3-5 times the volume of the tank per hour. For a 40 gallon tank, this would mean a flow rate of 120-200 gallons per hour (GPH).

However, if you have a large sump or a high head height, you may need a more powerful pump. To calculate the head height, measure the vertical distance from the water level in the tank to the outlet of the pump. Then add 1 foot for every 10 feet of horizontal pipe.

Here is a table of some common pump sizes and their corresponding flow rates:

| Pump Size (GPH) | Flow Rate (GPH) |

|---|---|

| 100 | 100-120 |

| 200 | 150-200 |

| 300 | 250-300 |

| 400 | 300-400 |

You can also use a pump calculator to determine the size of pump you need. Here are some popular pump calculators:

* [Aquarium Co-Op's Pump Calculator](https://www.aquariumcoop.com/blogs/articles/how-to-choose-a-water-pump-for-your-aquarium)

* [The Spruce's Pump Calculator](https://www.thespruce.com/how-to-size-an-aquarium-pump-1468727)

* [Petco's Pump Calculator](https://www.petco.com/content/petco-store/en_US/pet-supplies/fish/articles/how-to-choose-an-aquarium-pump.html)

Once you have selected a pump, be sure to follow the manufacturer's instructions for installation and maintenance.