While it might seem a simple concept to buy a pump for your water garden, when you start to look at all the options available, it becomes very confusing. However, with a little calculation and some common sense, it's relatively easy to buy a water garden pump for your yard's mini oasis.

Calculate your water garden's volume. Use the simple equation of width multiplied by depth multiplied by length. This will give you the volume of your water garden.

Contact a water garden supplier to find out how many gallons your pond will hold based on its volume.

Select the type of pump you prefer. Submersible pumps are best for garden ponds containing up to 1,000 gallons. Select a mag-driven pump instead of a direct-drive pump. Mag-driven pumps are more reliable. External pumps are suggested for larger ponds.

Pick the size of pump you need. The water in your garden pond should circulate once every two hours. If your pump is not heavy-duty enough, it won't circulate your water properly, causing your water garden's water to stagnate. Most water garden suppliers have charts to let you know the recommended size of pump for the size of your water garden. If you have fish, fountains or waterfalls in your water garden pump, you'll need to go one size larger on your pump.