That is turning the water over ever 1/2 hour.
here is some info not written by me..............lol
For example, if you had a 1000 gallon pond, then you will require a 500 GPH pond pump.
If you have fish, or accessories such as fountains or waterfalls/streams, you should account for this be getting a larger pump (preferably one size larger).
The general rule of thumb is that you should double the pump's capacity if you are planning to add fish. by this statement is sounds like your pump may be a little over sized, I am not sure it will harm anything, let some of the koi keepers tell you that, I don't do koi.
Calculating the proper pump for waterfalls is a bit trickier, because waterfall pumps are rated by both GPH and maximum waterfall height. To estimate your waterfall's height, you must measure the vertical height from the top of your pump to the top of your waterfall or stream. In addition, you must add another foot of height or lift for every 10 feet of hosing you will be using (this will allow for loss of volume from resistance within the hose). To calculate the required pump GPH, a general rule of thumb is that each inch of width of the channel will require an extra 100 GPH. For example, if your stream or waterfall spillway will be 10 inches wide, you will need a pumpthat produces an excess flow of 1000 GPH at your waterfall's height.
Pond Pump Sizing Chart
Pond Size (gallons) Minimum Pond Pump Size (for pond circulation only)
30-100 50 GPH
100-200 100 GPH
200-400 200 GPH
400-700 350 GPH
700-900 450 GPH
900-1100 550 GPH
1100-1500 750 GPH
1500-2000 1000 GPH
Recommended Tubing Diameter For Pond Pumps (When Connecting To Waterfalls)
* 1/2-inch diameter for flows up to 120 GPH
* 3/4-inch diameter for flows up to 350 GPH
* 1-inch diameter for flows up to 1000 GPH
* 1 1/4 inch for flows up to 1500 GPH
* 1 1/2 inch for flows up to 3000 GPH