Two pond pumps in a pond water feature are almost always better than a single pump. This might sound strange but it is true as I will explain.

Let's take my own personal situation ....

My pond is outside my bedroom window and I have a very nice waterfall.

At night the waterfall "noise" would keep us awake and we need our sleep. I switch this waterfall off every night and the fish do not suffer. They do not suffer because I have a much smaller pump feeding the
biofilter continuously. This second pump is not big enough to feed the waterfall.

Coming back to two pumps are better than one story.

The above description of my own personal situation essentially explains this. The major ongoing cost in a pond is electricity to run the pump(s).

To buy two pumps, if selected correctly, is often no more expensive than buying a single larger pump. However being able to switch off the waterfall pump (normally the bigger of the two pumps) can save an
enormous amount of money over the lifetime of the pond. The fish do not mind the waterfall being switched off most of the time and if you are at work you cannot enjoy the sights and sounds of the waterfall - so why waste electricity.

Furthermore if one pump does break down you can keep your biofilter alive by using the second (spare) pump.

My Excel calculators (free when you buy any of my books) will allow you to calculate how much you will be able to save by using two pumps in your pond. In the example I use in the calculator $309 is saved over 3 years.