A Glass Block Koi Pond / Fountain
This site describes a pond constructed with glass block. The water is held
in a liner supported by a metal frame. The glass block facade is back-lit
and does not actually contain the water. The following text and images
explain the construction.
Goals & Design Constraints:
- Create a showcase pond/fountain to be the focal point of the backyard.
All equipment (pump, UV, biofilter, leaf basket) are located underground
behind the pond so as not to distract.
- This pond is located on a hillside property. Leak prevention is paramount!
Because of possible leaks and unmaintainability concrete was unacceptable
for a water vessel at this location. Liner construction was used.
As gophers frequent the area the liner was placed in a large metal bowl.
- Minimal Soil Removal: above ground pond.
- Minimum Maintenance: quality components, giant leaf basket,
state-of-the-art biofilter, UV light, etc.
- Healthy Environment for Livestock: adequate size (2500 gallons),
good circulation (4400 gal/hr), state-of-the-art biofilter, large UV light.
- Energy Efficient: low current (2.5A 110VAC 4400GPH@10') pump,
no sharp elbow bends in plumbing, no check valves, most piping 2".
The site, before.
Site preparation begins July 2001.
Digging the equipment pit.
The equipment is installed in a brick-lined pit behind the pond.
The pit is 4' deep and is comprised of three levels. The lowest level
holds the biofilter and has a 3" drain at the bottom. The pump and leaf
basket are bolted on the middle level slab.
Laying out the plumbing.
Bottom of pit has 3" drain. Never pour cement without Rebar!
Pit almost swallows Dad.
Philosophy: If you can afford it - install only the best, and
- Aqua Ultraviolet Ultima II 5.0 biofilter rated for 6000 gallon ponds.
- Aqua Ultraviolet 80 Watt dual lamp UV rated for 7000 gallon pond
4000 GPH clarifying, or 2200-4400 gallons 3678 GPH sterilizing.
- Performance Pro Cascade C1/4-44 1/4HP 4400 GPH @ 10' head, 2.51 Amps.
This circulates 1.5X to 3X the recommended volume per hour for a pond
this size. The motor is a U.S. made Baldor, TEFC (Totally Enclosed Fan
- Aqua Ultraviolet Ultra Leaf Basket - a giant 26" tall x 9" diameter prefilter
- Plumbing - all 90-degree bends are long sweep elbows, most pipe is
2" and 3", most fittings are Schedule 80, flexible hose used for
vibration isolation is 100 psi braid-reinforced USDA Food & Beverage rated,
the only valve used is a 3" knife-type gate valve, all major components
installed using o-ring sealed union fittings, all metal fittings are
oversize it. The result will be lower maintenance, longer life, fewer
troubles, more time to enjoy the pond. Consider it an investment that
will pay off over time. (Save money by doing the labor yourself.)
Completed equipment pit.
Ready to pour glass block footing. Background: Pacific & Channel Islands
Four runs rebar in footing.
White concrete caps the footing.
Laying glass block - not for the timid!
Glass Block completed..
The glass block wall is backlit using rope light and reflectors.
The rope light is 110V, clear, and in a continuous length (~50 feet).
The U.S. made rope light, and its power cord, are UL approved. This is
especially desirable as this pond was permitted and had to pass electrical
inspection. (Everyone who got a permit for their pond raise their hand!)
If you have ever sold a house you may have found out that un-permitted
work 'comes home to roost' at the worst possible time. Even a missing
switch plate can stop a VA loan. Before I got the permit and began work
I had the building inspector come out and visit the site. This provides
an opportunity to ask questions, and to show the inspector that you care
about the process and about doing a good job. You want to have a good
relationship with him or her. They make the rules. It's not like you
can go to their competitor if you don't get along with them!
The rope light is held in a 1/2" aluminum angle that is attached to the
top inside edge of the glass block. 4-40 stainless studs were set in the
mortar to fasten the angle into place and to pinch-hold the rope light
into the angle. The aluminum angle was bent to fit the curve of the
glass block wall using a homebrew die in a milling machine vise. Holes
for the studs were punched with a Roper-Whitney punch.
Studs will hold rope light..
Rope light in place.
Rebar stakes being installed.
The liner is held inside of essentially what is a giant metal bowl.
The primary reason for this, or at least for the metal floor of the
bowl, is that this here is gopher country. They'd chew
through the liner in short order. The walls of the bowl also support
the liner and result in a several inch gap between the water containment
and the glass block. This gap is where the rope light is, as well as
the reflectors that back-light the glass block. Of course, it would be
neat if the water containment walls were actually the glass block
itself, but if that were the case one would spend the rest of ones
life trying to clean the algae off of the glass. The metal bowl acts
somewhat as a secondary containment system for the water, but is not
tested to be water tight.
Construction of the metal bowl begins by grinding the ribs off of one
inch of one end of each of 71 3-1/2' long 1/2" rebar stakes. These are
driven 18" into the ground in a 15' diameter circle within the glass
block wall - de-ribbed ends up.
A "story" pole is employed to keep the diameter in check. This 3/4"
EMT story pole was used throughout the project to meter diameters and
check levelness. The 2" fountain feed at the center of the pond was
the datum point from which all was measured. This pipe was roughed-in
just above ground level then fitted with a PVC pipe cap with a 1/4-20
stud set in the center. A Minerallac strap on the end of the pole
mated to the stud. Various widgets were fitted on the other end of the
pole to assist construction: to keep the glass block wall the right
diameter, to keep the rebar stake spacing in line, etc.
The rim of the bowl is a circle of 1" EMT. Approximately 5 ten foot
lengths of 1" EMT were bent in a curve to match that of the rebar stake
circle. This was one of those tasks that turned out easier than
expected. After the EMT was bent it was drilled through one wall with
a 1/2" diameter center bit, every 8". The de-ribbed ends of the rebar
stakes fit into these holes. Internal couplings were fashioned to
connect the rim segments. This rim makes the rebar stake ring
extremely rigid. The liner will be folded over the EMT rim to retain it.
The side of the bowl is a strip of galvanized sheet metal attached to
the inside of the rebar stake circle using Liquid Nails Heavy-Duty
Construction & Remodeling adhesive. This stuff is waterproof,
weatherproof, and extremely strong. The same adhesive is used to join
all of the sheet metal sheets used to form the bowl.
Sheet metal band installation.
EMT fits over ends of rebar.
Island and its base.
The island is one of those giant plastic flower pots turned upside-down.
It's about 2' tall, 2' in diameter at the opening (now the bottom), and
19" in diameter at the bottom (now the top of the island.) It sticks
above the surface of the pond by about an inch. The 2" pond water feed
is co-axial to the island and has a bulkhead fitting to pierce the
liner - which is draped over the island. So - the flower pot itself is
actually under the liner, thus has no tendency to float. The pot is
reinforced inside against side forces collapsing it. A concrete base
was poured for the pot, and dish-shaped with a drain near the center
just in case the bulkhead fitting leaks. This island drain empties to
the drain at the bottom of the equipment pit so the soil under the pond
doesn't get soaked. Along with the 2" water feed in the island are
several spare conduits for water, electrical, and whatever. It is not
anticipated that these will be needed, but if they are the top of the
island could be cut through to access them. The island is topped by a
glass disk, 3/8" thick 30" diameter with a 6" hole cut through the
center. This was fabricated by a local glass shop. I etched and
painted black the bottom of the disk so the inevitable algae wouldn't
show through. It gives a nice finished look to the island & fountain.
Forming the metal bowl.
Finished metal bowl.
Liner is installed.
Pond Lighting, continued...
The light from the rope light bounces off of reflectors positioned in
gap between the liner bowl and the inside of the glass block wall.
These reflectors are cocked so as to fairly evenly back-light the glass
block. They galvanized sheet metal 2' tall and 3' wide. The top of
each reflector leans against the EMT rim of the liner bowl, the bottom
rests at the base of the glass block. The bottom edges are trimmed
slightly with a tin snips so the reflectors lie in a curve that closely
matches the round pond. The reflectors are not otherwise fastened in
place so that they may easily be replaced. They are covered with
Reynolds Wrap Dazzle Holographic Aluminum Foil which adds just a touch
sparkle to the light seen from the pond wall, day and night. This foil
is available at grocery stores and is attached with spray adhesive.
Another Reynolds product adds a touch of color to the back-lit glass at
night. The rope light is wrapped with Reynolds Plastic Wrap, mostly
the blue tinted with occasional sprinkles of violet.
Holographic foil adds daytime color.
Tinted plastic wrap plus holographic foil add night color.
The fountain outlet in the center of the island is lit from within.
The water flows through 2" bulkhead in the center of the island and out
a 6" section of clear 2" PVC. I fabricated a light and threaded it
through the 2" line from the equipment pit, holding the light bulb at
the bulkhead fitting so the light bulb is not directly visible - only its
light. The bulb is a small bi-pin 12V 100W quartz halogen (type FCR).
Its pins are soldered to a length of underwater-rated type SOOW power
cord. That connection is potted with UV-6800, an underwater rated
sealant. The bulb, and the potted connection, are covered with a
special Teflon heatshrink tube. This assembly is threaded though a
waterproof cord grip and a 2" tee fitting just before the filtered
water exits the equipment pit. The light is operated at 25 Watts
half-wave DC via a diode and a 35 Amp 13VAC transformer. It's really
quite bright. (FWIW: I am an electronics engineer and a licensed electrician.)
Light rope wrapped w/colored food wrap..
Fountain light power passes thru Tee.
I built seven underwater fixtures that encircle the pond. They are
hooked over the liner and are positioned just a couple inches under the
water level. Angle-aluminum reflectors keep one from seeing the glare
of the bulbs. The effect is that the entire contents of the pond are
illuminated. The bulbs are 50W 12V quartz run at 6V and are packaged
similarly to the center fountain light.
View from above at night.
Capping the Gap...
The gap between the liner and the glass block is covered with
curves sections of lightweight concrete - like a bench seat.
I cast them using a mix of white portland cement, plaster sand, and
pumice. 3' sections weigh about 60lbs and are easily removable.
One side of each section rests on the top of the glass block.
The inner sides rest on the rim of liner bowl.
The rim of the liner bowl is 1" EMT over which is laid
two layers of polyethylene sheet, then the liner, then a cap made from
slitting a 47' length of 1" black vinyl tubing. This vinyl tubing
'snaps' over the rim covering and protecting the liner edge.
Mold for cap sections.
Tinted Lexan cover protects equipment pit.
Giant leaf basket.
Water lilies were potted in broad 5-gallon pots in aquatic plant soil
in hopes of keeping the water clear. Aquatic soil was topped by a layer
of washed river rock. aKwatik Lily Feeders were placed in each pot.
Pots drop into PVC pipe stands fashioned to position pots level and at
the correct depth. These stands will be shortened as the lilies grow.
A feeding ring was made from a scrap of drip line and a drip line coupling.
PVC pipe stands hold water lilies at right depth.
Pot at right depth.
I wasn't sure what kind of fish I wanted in this new pond. I don't
find the thought of getting deep into the Koi culture all that
appealing, i.e.: learning all of the classifications. It just doesn't
interest me. I especially wanted to avoid having animals that had been
bred for hundreds of years just for certain patterns of colors on their
backs - you have to give something up when you do that - like disease
resistance. A fellow ponder who I had consulted with on my plumbing
design told me about the drawer full of medicines he had for his Koi
and the hassle of keeping them healthy. He recommended goldfish, which
made a lot of sense. Then I came across Butterfly Koi and this
statement on the breeder's web site (Blue Ridge Koi):
"Due to their hybrid vigor they are stronger, more hardy, and more
disease resistant than either common goldfish or regular koi."
And, they're quite pretty. I'm sold! I've decided to make this
exclusively a Butterfly Koi pond. It should be said that this pond is
definitely not a purist Koi pond - its depth is marginal for Koi and it
contains plants, which are usually absent in serious Koi ponds.
So far all of the little guys have been purchased from FINS, a clean
and friendly pond & aquaria store in Camarillo California.
FINS Aquarium & Pond Specialists
2175 Pickwick Drive, Camarillo CA 93010, 805-389-1128
The pond has a semi-bottom drain. Because the pond location cannot
tolerate leaks I did not want to risk a conventional bottom drain.
Repair of such a drain would require tearing up the pond. I opted for
what I call a semi-bottom drain. A 2" ABS pipe circles the bottom of
the pond just inside of the outer perimeter. A 3" bulkhead pierces the
liner about a foot up from the pond floor. This 3" makes a sharp 90
down into the pond to tee into the 2" ABS circle. On the "dry" side of
the liner the 3" makes another sharp 90 down into the ground and makes
its way into the equipment pit and a 3" knife valve. Back inside of
the pond every couple inches a hole is drilled in the 2" pipe circling
the bottom. The third of the circle farthest from the exit bulkhead
has a 1/2" dia hold drilled in it every 2". The third of the 2" pipe
nearest to the bulkhead exit has 1/4" holes every 2". The remainder has
3/8" holes. This is an attempt to draw water into the drain equally
all around the diameter of the pond. There are no stagnant corners for
ammonia or toxins to linger. Another detail - the sharp 3" 90's are
actually 3" ABS Tee fittings as they are more compact that regular 90-
degree fittings. One leg of the tee that is inside of the pond (the
tee that connects to the drain encircling the pond) points up toward the
pond surface. This tee is reduced to 1/2" and stops a few inches below
the water line. This open 1/2" port should act as a siphon breaker if
something breaks in the below-water-level equipment pit resulting in no
more that half the pond water siphoning, or being pumped, out.
One issue of above-ground ponds is the loss of the insulation value of
the soil that would have formed the sides of the water vessel. The
Pittsburgh Corning Premiere Series block used for this pond has an
R-value of 1.96. This, in addition to the 8" air gap between the glass
block and the water vessel, are probably roughly comparable to an
in-ground pond. Fortunately, at this location it never gets cold
enough to freeze anything more than a thin film of dew, and even that
occurrence would make the news. For more information on the glass
block used visit:
Pittsburgh Corning Corporation, http://www.pittsburghcorning.com
Status... (December 28, 2002)
The pond has been wet for five months now. Here are some observations:
The water has never been anything other than crystal-clear. I chalk
this up to:
1) The more than ample UV light.
2) The fact that the water lilies are potted in aquatic soil, not dirt.
(If you don't want dirt in your pond, then don't put dirt in it!)
3) Everything that's gone into the pond has been washed and sterilized.
4) The pond is only 5 months old.
The Aqua Ultraviolet Ultra Leaf Basket has been a real winner.
It doesn't need cleaning even weekly, and it could probably go a month.
The Aqua Ultraviolet Ultima II 5.0 biofilter has also worked out well.
So far it needs only one minute of backwash and one minute of rinse
once a week.
One of the last things I did was to build the underwater lights.
They contribute a lot to the pond. Everything in the pond is visible
at night instead of it looking like a black pit.
The plants have not done well. I believe this is due to several reasons:
1) The late start (September/October) in planting.
2) The water lilies got caught for a week in Ag inspection between
the supplier in Colorado and here, which didn't help their health.
3) The pond is too clean and devoid of nutrients.
4) The city water is extremely alkaline (high KH and pH).
5) Microscopic larvae have attacked some plants.
Now that I recognize these problems (3-5) I am working on solutions.
I'm adding potash (potassium), aquatic plant stimulant (trace elements),
Koi Clay, and Dipel biological control for the larvae.
The equipment pit has a serious condensation problem when its cover
is in place. Moisture condenses on the plumbing and the bottom of the
Lexan cover resulting in rain inside of the pit. I'm working on
elevating the cover slightly to provide some ventilation.
Status... (May 21, 2003)
Still never any 'pea soup' algae, but string algae has been a problem.
Lost one Koi to a Heron. Scarecrow sprinkler now installed.
Only once measured a trace of ammonia since the pond was built.
So far no problems at all with plumbing, biofilter, UV, pump, etc.
Status... (August 1, 2003)
Pond one year old today.
Discarded the Akwatik fertilizers. They constantly clog with fertilizer
tabs. They are not large enough in diameter - especially at the elbow.
Better off to make one's own with larger diameter pipe which should be
large enough for two tabs to lie side-by-side.
Not able to get Water Hyacinths to survive more than a month or two.
I've tried adding potash, iron, Epsom salts, aquatic stimulant - they
Status (6/05)... Okay, now it's fashionable to call this a Blog!
- No change with Water Hyacinth luck. They still live only a month or two
no matter what I do. Now realize many other ponders have the same problem.
- Had bad case of murky pond water. Kind of brown/yellow/green.
Found UV ballast dead as well as one of the two 40W UV lamps out.
Pond cleared in a few days after that was fixed. Shame on me for not
checking the UV when the problem started. Otherwise have never had any
'peas soup' algae.
- Have had a strange algae that grows up from the bottom of the pond in
columns. Water flow not quite strong enough to break it up, but it's
not as strong as string algae/blanket weed. AlgaeFix takes care of it.
- Only one incident of fish disease so far, Anchor Worm. Two Dimilin
treatments licked it.
- Should have had the glass disk on top of the island made from black
glass. I etched and painted it with 'waterproof' glass paint, but
the paint eventually comes off.
- I have installed a 22-inch polycarbonate sphere for the fountain
sculpture. I now consider the pond 'finished'!
I have installed an air pump, air line, and air diffusers. Think it's
time to add some aeration as the koi population is growing, although I
haven't had any problems with low oxygen levels (yet). I circled
the base of the island with air diffuser hose. Works great.
- So far koi have not bothered the water lilies at all.
- One of my favorite pond supply dealers is Drís Foster & Smith.
Pretty good prices, nice catalog, good selection. But... have
received three shipments from them containing liquids
that leaked (one even with most the liquid frozen solid!) They have no
problem replacing damaged shipments, but wouldnít it be better to
tighten the bottle caps and tape them closed to begin with?
- Adams Aquatics has also proven to be an excellent supplier.
- Biggest pond supply dealer complaint I have is no one carries
everything I need. I always have to order from two, sometimes three
dealers to get the supplies I use. For example, no one carries both
Dainichi Koi food and Sho Koi Koi food. I feed both so have to order
from two different outfits.
- Second biggest complaint is poor packing. Example Ė packer puts
items in box, then pours packing peanuts on top of them. Might as
not use any packing materials at all! The right way Ė fill box 1/3rd
with packing peanuts, insert items, fill rest of way with peanuts and
then a little more, seal box. This locks the items in the middle of
the peanuts so they donít drift down through them in transit.
- Have been feeding 50-50 mix of a Dainichi food and Sho Koi.
Fish have always been healthy and grow fast. Those in the local Koi
club have always complemented me on the fish. I think the quality food
has plenty to do with this. Dainichi is expensive, but worth it.
The vitamins, etc., are coated onto the pellets after baking so
their nutritional value isnít degraded. Made in the US, and is
supposed to be the only Koi food exported to Japan.
- After four years Koi and water lilies cohabitating just fine.
- Koi have had offspring twice now. Given many away to local club members.
- All thru summer have water clarity problems. Think thereís maybe just
too much organic matter in the water from seven water lilies. May
cut down on the number of water lilies next year and see what happens.
- Contacted earlier this year by an author working on a Koi for Dummies
book who wanted photos of the pond for the book. The publisher, Wiley,
would never send me a photo release form so nothing came of it.
- I wrote an article on the pond that was printed in the Jan/Feb 2006
issue of Koi USA Magazine
Other links that may be of interest...
Round Patio with Custom Tiles:
Round Patio with Custom Tiles... http://www.kissingfrogs.tv/newpatio.html
A White Light Emitting Diode (LED) lit Patio Cover:
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Homemade Light Emitting Diode (LED) lit Yard Lights:
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Details of a unique bamboo and gilded copper garden trellis:
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An Illuminated Glass, Gold, and Copper Birdbath:
Glass, Gold, and Copper Birdbath... http://www.kissingfrogs.tv/birdbath.html
Fish Wind Sculpture:
Fish Wind Sculpture... http://www.kissingfrogs.tv/windsculpture.html
Easy Feeding Water Lily Pots:
Water Lily Pots with Integral Feeding Tubes:
Easy to Feed Water Lily Pots... http://www.kissingfrogs.tv/lilypots.html
Painted glass block landscape light project:
Painted Glass Block Landscape Lights... http://www.kissingfrogs.tv/blocklights.html
A unique 97-foot long fused glass-on-brick project:
97' long fused glass-on-brick project... http://www.peltier-info.com/wall.html
Directory of over 120 pond supply dealers:
Pond Dealer Directory... http://www.kissingfrogs.tv/ponddirectory.html
A permanent Heron-deterrent Scarecrow installation:
Heron-deterrent Scarecrow Installation... http://www.kissingfrogs.tv/scarecrow.html
Homemade Glassworking Lathe:
Homemade Glassworking Lathe... http://pw2.netcom.com/~sjnoll/glasslathe.html
Largest Thermoelectricity information site on the 'net:
Thermoelectricity information site... http://www.peltier-info.com
Largest used high-tech equipment dealer directory on the 'net:
Largest used hi-tech equipment dealer directory... http://www.big-list.com
LED Light Emitting Diode spectral scans and measurements:
LED Spectral Scans... http://www.big-list.com/leds.html
email: s t e v e @ k i s s i n g f r o g s . t v
(C) 2004-2019 Steve J. Noll