Question
QUESTION: Good Morning, John.  Thank you for your previous help on one of my questions.

There has been some controversy over how much to run our pond pump.  As stated in my previous question, our pump with Skimmer box and BioFall runs 4 descending ponds, with a large pond at the bottom.  (8,500 gallons)  The landscaper that built our pond, said we should run our pump 24/7.  He said that this will reduce any algae build up and keep the "pump primed."

I do not agree with this.  I do have small Koi in the pond, but the surface area of the bottom pond is so large, there is plenty of oxygen for the fish, if the pump is shut off overnight.

Running a 1 horsepower pump all day, every day, in these days of higher electric bills; can run close to $100 extra per month. I have heard that others that own ponds, also suggest running the pump all of the time.

What are your feelings on this subject?  Again, I appreciate and trust your advice, since you have been in the business for so long.

Very Sincerely, Heather

ANSWER: Heather,

The purpose of the rock and gravel in the pond is to support a large population of Ammonia and Nitrogen converting bacteria.  The bacteria converts the wastes that the fish excrete into the water into Nitrates that the plants can absorb and remove from the pond.  This process removes the nutrients from the pond and starves the planktonic algae that causes the water to turn green. This algae dies and settles out and the water clears.  This is the process that actually clears the water more so than the "filters" that we install.  They remove a little of the suspended matter, but mostly they are homes for additional concentrated bacteria populations and it is the bacteria that actually causes the water to clear, not the "filters".

Now, having explained all that, in order for this process to work at top efficiency, the water has to be moved passed and into contact with the bacteria since they can't move.  The more often the water is moved, the better it all works.  This is why you want a big pump and lots of water movement.  And the bacteria that make all this work are "aerobic" bacteria, meaning that they have to have oxygen to live.  When you cut off the pump for more than a couple of hours, all the bacteria in the filters suffocate and die and you have to start all over again.  So, you really DO need to let the pumps run 24/7.

Hope this helps,

John



---------- FOLLOW-UP ----------

QUESTION: John,

Will the Koi really "learn" to stay away from the intake of the skimmer?  Even though I have taken precautions, I do worry since these are only 3 inch Koi, that they will become trapped between the intake and the mesh?  

Answer
The koi really will learn stay out.  They'll only get trapped when they are weak or sick, or if your pond level gets low and the get sucked in.  Put a screen over it for a while just to be sure if you want.  But this negates the skimmer action.

Good luck

John