We have a 1800-2000 gallon pond with 4 koi. We have two pumps
running to a biological filter and want to replace the two
pumps with one big one and also add a UV filter. We came across
a calculation for figuring out how much a pump puts out per
hour but cannot seem to find it now. We want to figure out
what the equivelant of the two small pumps would be to give
us a better idea on what size should be for the one big one.
The calculation we saw was to fill a five gallon container
and to time how long it takes. One pump took 45 seconds and
the other took 1 minute. The two together took 27 seconds.
Do you know of this calculation or a different one?
One other question is, we have well water and the "general
extremely high. What are your thoughts on lowering the hardness
to an acceptable level.
Pump #1 is easy. 5gal/1min x 60min/hr
Pump#2: 5gal/0.75min x 60min/hr = 400gal/hr
Doing the same math with your combined
flows gets you roughly the same number (actually a little
Either way, it is inaccurate, because it
does not take
into account how high you are pumping this water to
get to your falls, how long your pipe run is, how many
elbows you have in the run or the diameter of pipe you
are using. Each one of these parameters adds friction
and reduces flow.
In any case, you are severely under-pumped
of the box. The goal in biofiltration is to present
each molecule of water in your system to your
biofiltration media at least once an hour. For optimum
bioconversion, your pond needs a pump that can deliver
2000gal/hour from your pump inlet to your falls,
measured at the top of your falls.
Most good pumps come with a graph indicating
flow loss per foot of "head" (how many feet above
water level you are lifting the water) I'm sending along a
series of tables that
will help you estimate how much estimated "pressure head"
you need to add to this number to calculate what any prospective
pump you are thinking of buying will actually deliver to your
Remember that your filters will also add
especially if it is one of those commercially produced
canisters with teeny-tiny inlet and outlet ports. It
is actually a great idea to maintain the same pipe
diameter throughout your system, and many advanced
hobbyists actually increase the diameter of their pipe
runs as they get further from their pumps.
The only problem that hardness will give
you is a tendency for your kohakus to develop little black
dots (called "shimmies") and your kawarimonos to
go black in your water. This isn't dangerous to koi health,
only dissapointing to the ardent hobbyist who just went to
Japan and brought back a $10,000 fish which is now speckly
and will *not* win Grand Champion. Don't worry about it, and
don't get seduced into adding chemicals or hooking up a water
softener (which only adds salt) to try to change it. That
way lies madness.
(Answer courtesy Bob Passovoy)