Koi Dome!

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Last October we had an early hard freeze. The pond froze over except for the air hole and waterfall. My wife got very worried about the fish being too cold and us not being able to keep an eye on them. I was talked into making a PVC and plastic dome over the pond. It has worked very well and I want to share our experience with you.

Our home in Santa Fe is Zone 5-6, nights to -5 degrees this time of year and already about 14" snow as you can see on this Jan 1 picture. The outdoor air temp 1/1/01 was 05F at 7AM, inside the dome the air temp was 72 at 2PM! The water temp is a very constant 45 the past few weeks. As the days lengthen I suspect the water temp will get up to 55. The air temp inside the dome will fall below freezing during the night this time of the year so you can not leave delicate tropicals in the dome with our type of climate. There is no extra heat, no ice at all. It is so nice to be able to go into the dome and see all the fish, be sure there are no ulcers or other problems. I covered the upper pool and waterfall also. This allows the filter system to run all the time without chilling the water. I am sure this will reduce the normal spring stresses on a pond. There is a nice growth of algae for the fish to munch on and keep water quality high. Our water lilies are even putting up new leaves!

On 1/13/01 we had a beautiful  snow in Santa Fe. The storm started with 30+ mph wind then it got still and we had 8" new snow. The dome had no problem with either the wind nor the snow. In this picture the top has been swept off to unload the plastic.

The water temp on the surface today was 43, 2' down 45 and on the bottom (4') it was also 45. The fish were swimming around like nothing had happened.

Very pretty out and the skiing was great also! 

The dome is made of 3/4" PVC ribs bent over 1/2" steel re-bar driven into the ground. The re-bar is easy to drive into frozen ground and will be easy to pull up in the spring. Very few joints are glued so it can be taken apart. In the center (top) of each rib there is a 4 way cross connector of PVC. A center ridge pole runs between each rib, connecting at the cross connectors,  to hold the ribs upright and straight.  After our first snow the dome collapsed into the middle giving a M appearance. The plastic kept the snow and cold water separate from the pond water. I was able to brush and bucket the snow/water off the plastic and the PVC bounced back to its original shape, no damage. To prevent this I went back and put in 1" vertical PVC columns to hold the ribs and ridge pole up. With this the pond has done well with 45mph winds and a recent 6" snow! 

This shows the top of the dome where the cross connector joins the ribs and the ridge pole (on the right of the picture). The T connector joins the 3/4" ridge pole with the 1" vertical column to help hold the dome up. Each rib is made of two 10' 3/4" PVC pipes that join in the middle at the cross connector. This easily spans the pond which is about 14-15' wide and 25' long. There is about 4' from water level to the top of the dome. This allows room to move around the sides and enjoy the space.

The vertical 1" columns sit on pads made of PVC so as to not punch a hole in the liner and to provide lateral stability. These joints are glued for strength.

With one helper, good clipper type PVC cutters and the material the project can be done in about 4-5 hours. A very irregular shape will slow you down. Waders are helpful for working the middle sections but most work can be done on dry land. 

Near the end of the pond the center ridge line is too close to the drop off shelf to allow for a pad on the bottom. At this point I put in a 2" horizontal pipe that spans the width of the pond and sits on either shallow side of the pond. A T connector supports the column. The pond deicers are not needed, a left over from earlier in the winter! We had 6" snow Christmas day and no problem with collapse.

At the ground level I put a 4 way cross connector over the re-bar. The spanning rib goes into the top of the connector. Off of each side of the connector is a length of PVC that runs to the adjacent re-bar/rib connector. This makes a perimeter of PCV along the ground. The plastic is wrapped under the PVC from the outside to inside. Special PVC plastic sheet clips hold the plastic cover in place. I used many clips, about 40, on our 25X15' pond. The clips are also used on the ribs to reduce flapping in the wind. I used the shorter 3" clamp size. No failure so far but in high wind areas you can drill the clips and screw in a wood screw for better hold. From the outside this give a neat appearance, the extra plastic is on the inside and not seen. Be sure to allow plenty of extra length and width! This 4 way cross was glued to the rib pipe because there is a tendency for the dome to lift up in high wind. This clued joint prevents this. The other joints are compression only so it will still come apart in spring. Note the nice green grass!

At the back end the dome ends with the last rib. This leaves a vertical sheet of plastic for a door. I put in a zipper door. The sticky material on the zipper isn't very strong especially in cold weather! I was able to use a home stapler to staple the zipper to the plastic. This has worked very well. It is really nice to be able to easily get into the dome to sit and watch the fish. We have even had picnics by the pond, warm moist air and the pond is a nice change from the outdoor winter! I put an extra flap of plastic over the end with the zipper to relieve wind stress and reduce air leaks. This extra flap is held in place with the clips. The bottom is extra long and I roll a 2X4 board up in the extra plastic to hold it down.

The off center vertical support at the end illustrates one of the problems with a hoop/rib design. If each hoop isn't the same length or if each half of the hoop isn't the same length it is difficult to get the height and position of the center ridge pole equal along the length of the dome. At this end the left side of the rib is shorter than the right because of the sidewalk. I could not make both side equal length. The angled vertical pipe helps hold the center ridge pole in the correct alignment with the rest of the dome.

Ideally you would have a rectangle with all the ribs equal and the center ridge in the exact middle. Then when you bow the ribs the shape will be equal. If this can not be done you can compensate with some careful trimming of the ribs and repositioning of the re-bar. This is slow trial and error but will work. 

At the front end of the pond the center ridge pole bends down to the ground similar to the ribs on the sides. This give the end facing the prevailing winds a pointed bow to help shed the wind. The bowing over also provides some lateral stability.

The plastic is extended over our top pool and waterfall. This really helps keep the water warm and allows me to run the pump and filter all winter. This should reduce early spring shock. There is a nice growth of algae for the fish to munch and to help keep water quality high.

I started with cheap construction 6mil plastic. This was good to experiment with, check size and shape etc. I have now put on good quality greenhouse grade plastic. It is much clearer, allows more heat in. The premium type also has an infrared reflector to further trap heat. This plastic cost me about $125 with shipping for 50X25' ( I had to buy 100' but sold half to a friend). Be sure your plastic is wide enough and long enough!! The other material cost about $100, not too much all considered.

Here are some of our fish enjoying winter. They swim much more and use the entire pond now that the dome is in place. No longer are they stuck on the bottom in the deepest part of the pool!

Wendy in Ca tried a dome and wrote this"

My clip supplier was A to Z supply 13396 Ridge Road, Grass Valley CA 95945 Phone  530-273-6608  FAX (530)273-0892 They are also on the internet http://www.atozsupply.com/

The plastic came from Tuefel Nursery Portland OR (503)646-1111 or web http://teufel.com  I am unsure if they still sell the plastic. Their web site is being redone and you will have to call them. 

Morton's also sells a full line of plastic. They are in TN, 800-473-7753 or web site http://mortonproducts.com/page.cfm/3048 or their Home Page

Shipping the plastic can be fairly expensive so you may want to look for a site closer. Lots on the wed under plastic and greenhouses.

If you have questions feel free to e-mail me. If this was helpful please let me know. These web pages are lots of work and it is nice to know if anyone looks at them!

Brad Stamm

Santa Fe NM

mailto:rbstamm@ix.netcom.com