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/Aquatic Gardens, Design, Construction & Maintenance

Converting Swimming Pools, Spas to Biological Ponds


by Bob Fenner  
Aquatic Gardens

Ponds, Streams, Waterfalls & Fountains:
Volume 1. Design & Construction
Volume 2. Maintenance, Stocking, Examples

V. 1 Print and eBook on Amazon
V. 2 Print and eBook on Amazon 

by Robert (Bob) Fenner

Imagine (finally) having enough space, volume in your water garden to do all the planting, fish stocking, culturing you've ever wanted. What, you say, there's no room back there with the swimming pool. Well, this is exactly the body in question. You can convert your only-infrequently used pool to a gorgeous maxi-sized water feature.

Most of the real work in this endeavor is already done. The hole dug, spoils hauled away, plumbing and electrical in place. What is required on your part are a dream/plan of what you want your new-found pond to look like and do, and a bit of clean-up and mechanicals modification. Having done a few of these conversions through our companies years back, I'll gladly give you our "steps to completion" and insights as to whys and wherefores for such an operation.

In the Beginning There Was'¦ A Pool:

Do you have a swimming pool that nobody uses much? It's likely of Gunite and reinforced steel construction, but even if it's a liner pool , or in need of re-plastering, re-tiling you can practically convert it to a Koi pond or water garden. Don't worry too much re the existing "mechanicals" (cartridge/diatomaceous/sand filter, pump) that's in place. We will go over their consideration of continuing use and/or replacement.

Cleaning the Existing Basin, Plumbing, Mechanicals:

A chief concern in converting a swimming pool to a working biological water feature is the removal of extant chemicals and residues from their surfaces. As you likely know, pool chemicals like cyanuric acid/conditioner, sanitizers (chlorine, bromine), are general biocides, killing all forms of life. These need to be thoroughly removed.

There is a S.O.P. (Standard Operating Procedure) called "Acid/Bleach Washing" utilized in both swimming pool and ornamental aquatics interests to do exactly this. Acid/bleach washing entails dumping/dewatering the system, applying a water-diluted solution (about one tenth 3 Molar Hydrochloric, aka Muriatic Acid) to the basin surface, plumbing and mechanicals surfaces (remove filter cartridges first), rinsing , draining'¦ and one more time rinsing and draining this wash to waste. (The actual Action Plan for this "Acid/Bleach Washing" procedure is stored on the WWM site here: http://wetwebmedia.com/acidblchpnds.htm>

Do be careful in planning and executing these acid/bleach washes. Wear rubber gloves, long-sleeve pants and shirts you don't particularly care for, and eye protection. Like so many things in life, once you've done this cleaning it will seem simple, straightforward. If you don't have the time, inclination, use your phone-dialing finger to locate a pond service or even swimming pool company with experience, tools and materials to do it for you.

Basin re-coating, plastering and re-tiling are generally non necessary, as the coating by algae et al. will hide all. Just take care not to slip and slide in the now-pond should you have occasion to step into it.

About Pumps/Pumping, Circulation, Aeration:

As with choices between "fish ponds" versus reflecting pools, lily ponds'¦ there is a wide-range of considerations in how much pumping you will likely want and have to do to keep your new conversion "clean". For full-blown Koi (Nishikigoi) systems, there is a need to run the pump continuously. Very likely, the pumping mechanisms in place are not the best available, most appropriate technology to use with your conversion. Most fully-rated swimming pool pumps are designed/engineered to produce relatively high volume at high pressure. What you will likely want is some volume, at not much pressure'¦ particularly in our world of escalating electrical costs. Do your homework here, as there are some very good choices in fractional and multiple horsepower pumps for ponds that can be readily fit to the existing pool-now-pond plumbing. Compare power-curves, water moved per kilowatt consumed, service factors'¦ as the pump operation cost will very likely be your highest investment ongoing.

On the other hand, if you will only be operating your waterfall etc, when your rich uncle comes to visit, or this will be a reflecting or more planted water garden, you may well be fine with sticking with your current pump, operating same manually or for a few minutes to hours daily on a timer. Comparisons in costs of acquisition, maintenance and operation need be made, much as with a question of whether or when to trade in your old car for a new one.

Water movement, circulation needs are likewise a more/less issue. For Koi, other vigorous users of oxygen you may need to turn the water over quite a bit, for plant-mainly systems hardly at all. Destratification systems have been discussed here (Water Gardening Jan/Feb. 2001). In most cases, folks continue to utilize the "main drain" on the bottom of their pool/water garden as their pumps principal intake (rather than supplying another mid-depth intake). If you move your water around regularly (as in daily) and are up on maintenance (removing mulm, leaves) you will likely not have difficulties with "stagnant water" or stratification in your system. If freezing of lines, water in gear is a concern, you would do well to consider de-icing mechanisms, surface agitation, air-lift mechanisms, use of a small submersible pump for keeping your water moving top to bottom.

About Filters/Filtration:

By intent swimming pool filters are made to remove small amounts of small materials from the water. Biological ponds contrarily call for extraction of larger quantities of mainly larger matter. Some folks will try to continue using their swimming pool filtration, but this almost always inappropriate, non-functional, getting clogged quickly, necessitating frequent (very) cleaning, backwashing'¦

If you are fortunate to not have much leaf litter, good co-filtration from aquatic plants, perhaps a bog area'¦ you might be able to simply remove the existing filter media (DE sleeves, cartridges, sand from sandfilters'¦) and replace this media with others of more suitability. Plastic biomedia, ceramics, fused glass beads'¦ to batting material (filter pads, Dacron/polyester) from the yardage store or pet-fish purveyors might well go in place of your existing filter's "guts".

For Koi ponds, other more serious "ponders" a "for ponds" filter is called for'¦ perhaps a large container/sump built inside a new waterfall? Maybe an inline (series) of troughs like the fine ones made by Rubbermaid "¢. Even in-pond filters (now that you have all the space) can be considered, though these latter need to be well thought out to expedite maintenance, including periodic removal, cleaning.

About Plumbing, Skimmers, Vacuuming:

In some cases you may need, desire to add plumbing'¦ for added intakes, discharges like water falls, to improve circulation, allow for the passage of more water w/o resistance. This almost always should be constructed of schedule 40 PVC pipe and fittings. Copper pipe that is already in place is almost assuredly no problem to your livestock, due to coating with age, the very little copper ion released will be complexed/precipitated, of no consequence.

Should you have a heater for the swimming pool, it and its plumbing can be ignored as well, or removed, retrofitted around to lessen pumped water drag/resistance.

Skimmer intakes can be problematical in pool to pond conversions'¦ A great deal of floating matter and even fish livestock can become fouled in such areas, and need to be screened to prevent such tragedy. Plastic mesh of sturdy construction can be resourced within these pages, cut and fit over skimmer intakes.

Should you find yourself cutting into your existing pump's plumbing don't miss the chance to "cut-in" barbed intake and discharge fittings on tee's, valves on the new pumps intake and discharge lines. These can be a real boon in regular vacuuming maintenance and occasional, larger water changes, allowing you to pull out the water and place the waste where you want it.

About Maintenance:

Is more or less the same as regular size, shaped biological ponds. Feeding of fishes, other animal life, potting, re-potting, fertilization of plants follow the same annual and sub-divided schedules.

And Then It Was'¦ A Water Garden!

Really, there you have it. An exciting adventure that will "net" you many hours of enjoyment and tranquility'¦ from a lifeless cruel maintenance taskmaster of a swimming pool, to a bonus sized water garden.

Bibliography/Further Reading:

Speichert, Sue. 2001. A breath of fresh air. Mechanical aeration units return life-giving oxygen to pond water and can add aesthetic value at the same time. Water Gardening  2001.

Aquatic Gardens

Ponds, Streams, Waterfalls & Fountains:
Volume 1. Design & Construction
Volume 2. Maintenance, Stocking, Examples

V. 1 Print and eBook on Amazon
V. 2 Print and eBook on Amazon 

by Robert (Bob) Fenner
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