Pond Construction Do's and Don'ts

Submitted by Don Harrawood on Sat, 10/08/2016 - 09:09

By:  Don Harrawood, SKAPA

There are three basic types of ponds, Water Features, Garden Ponds, and Koi Ponds.  The differences are quite obvious when discussed.  A water feature is merely a fountain or a small pond that circulates water for beauty and provides the soothing sounds of a waterfall.  Most water features do not have fish because the water contains a high level of chlorine (which kills fish) to discourage plant and algae growth.

Most ponds are called garden ponds.  They are generally constructed about 1.5’ to 2.0’ deep, use a liner for water containment, and are filled with rocks or gravel.  Typically these ponds have shelves along the sides to support water plant vegetation.  A waterfall and a skimmer at opposite ends of the pond provide the total water circulation in the pond.  A submersible pump located inside the skimmer provides the pumping power. 

Disadvantages of the garden pond for Koi keepers are numerous.  A few are as follows:

  • Water at the bottom of the pond becomes stagnant, since all the water circulation is moving top water into the skimmer and pumping it into the waterfall.  There are no bottom drains.
  • Rocks and gravel in the bottom of the pond collects debris that decays and cannot be removed without removing the rocks and cleaning the pond.
  • Shelves along the sides provide a platform for predators to damage or kill fish.
  • These ponds have no filters or ultraviolet lights for providing good water quality.  The fiber pads in the skimmer catch only the large debris.  Without filtration, most of these ponds will have algae blooms and green water in warm weather.

Now let’s discuss Koi Ponds.  A true Koi pond possesses most or all of the following attributes.

  • Pond is designed and shaped to eliminate dead spots in water circulation.  This is the elimination of little nooks and crannies that will have no flow and will become stagnant.
  • Pond has smooth bottom so that drains can pull excess settlement materials from the pond bottom.  Eliminate stones and rocks.  These impede water flow along the pond bottom and provide traps for detritus and mulm.
  • Water depth should be a minimum of 2 feet deeper than the Frost Depth of that area to protect Koi from cold in the winter, sun burn in the summer, and give them room to escape predators.  Pond sides should be straight down, with no shelves along the edges.  This also protects from predators.
  • Koi ponds may have liner versus concrete construction.  Both types of water containment are good, and each has their own short comings.  Liners are less permanent and can be easily torn if not handled properly.  They should have an underlayment (old used carpet) for protection from damage when someone walks inside the pond.  Liners come in many types of materials.  The very best and recommended liner material is EPDM rubber of 45 mil thickness.  Liners generally have large folds when they are assembled.  These folds sometimes are unsightly, and can trap decayed debris.  Concrete ponds are more permanent, but they also are more prone to cracking, causing leaks.  Some cracks could be easily repaired with pool epoxy putty, which can be used under water.   In severe cases, the pond may need to be drained, cleaned and then repaired.  New concrete ponds are always a high pH problem unless they are sealed with a non-alkaline sealer that is safe for fish.  Without this sealer, the water leaches the cement out of the concrete, raising the water pH to a dangerous level for fish.  If not using a sealer, the pH must be reduced with acid which could take several weeks, of if using a quick acid method, then the pH must be raised again after the treatment. A digital pH meter is nearly mandatory for checking pH during the treatment.
  • Bottom drains, also known as bottom suction ports, are a must in Koi ponds.  Without them, the pond bottom water becomes stagnant and resulting decayed materials cause hydrogen sulfide gas, which is poisonous to fish.  Bottom drains are needed to help keep the pond bottom clean.
  • A skimmer is desired to trap floating materials.  Skimmers are not a necessity if the pond owner chooses to skim the pond by hand.  Either way, the floating materials should be trapped and disposed of in order to reduce the amount of settlement inside the pond.
  • A waterfall is desirable for sound effects, but waterfalls are also a prime method used to aerate (supply oxygen) the water.  Aeration can be accomplished by other means such as by streams leading into the pond, and by using a commercial aeration device such as a venturi or air pump with air stones.
  • Koi ponds should have good filtration.  There are many types of filtration on the market, such as vortex chambers, bead filters, and Ultra media filters.  Some pond owners make their own filters from various materials.   Swimming pool sand or D.E. filters are not recommended for Koi ponds because residue from the fish cause sand filters to crust over and tends to solidify the sand and cannot be properly back washed.  A biological convertor is needed in Koi ponds.  These convert ammonia (a by-product from fish respiration and fish waste) into nitrites and then into nitrates (less harmful to fish and very beneficial to plants).  Both ammonia and nitrites are harmful to fish.  Most mechanical filters also become bio convertors after a short time in operation.  Other types of bio conversion are numerous.
  • U.V. Lights (Ultraviolet Lights) are used primarily to control green water algae.  These lights, when properly installed, kill the algae, which clumps together and can be filtered out by mechanical filtration.  U.V. bulbs must be changed every 12 months in order to remain effective in killing algae.
  • Pumps and plumbing should be sized to accommodate the water flow needed for a pond.  It is generally recommended that water flow per hour is equal to or exceed the total pond volume in gallons.  Pumps can be submersible or external type pumps.  Both work effectively; however the pond owner should be knowledgeable of the amount of power consumed by pumps.  Pond pumps are low pressure/high volume pumps that pull considerably less amperage (and are thus much cheaper to run) than pumps designed for swimming pools.
  • An Auto Fill Valve is used to keep the pond to a constant water level while compensating for evaporation and small pond leaks.  These are desirable, but not necessary if the pond owner wishes to fill the pond with a hose.  When a considerable amount of city water is added at one time, de-chlorinator should be added to eliminate chlorine added to the pond by refilling.  Chlorine is a very potent killer of Koi.
  • Pumps in Koi ponds should operate constantly except for when minor maintenance is performed.  Clear water is not necessarily quality water; therefore pond water should be tested for ammonia and nitrites on a regular basis and corrective measures taken when these are detected.   Constant aeration is vital in summer months, since warm water does not hold as much oxygen as cooler water.  Koi can die rapidly when water flow and aeration ceases for just a couple hours during the warm water season of the year.   It is a good idea to have an air pump aerator on hand for emergencies.  Consider another alternate aeration method when systems fail, hydrogen peroxide (available at Walgreens and other local stores) can be added to the pond water to supply oxygen.  A dosage of ½ cup of 3% hydrogen peroxide (H2O2) per 100 gallons of pond water, will provide oxygen for approximately 4 hours.  For example, in a 2000 gallon pond, 10 cups of hydrogen peroxide every 4 hours will be needed until the emergency has ended.

!If you're not havin' FUN, you're not doin' it right