Garden Endeavors

Perfect Water

You have a Watergarden. let's assume that this infers that you have both plants and fish living in it. Let's also assume that you know that lots of plants are good and that it is important not to have too many fish. Let's assume you are also attuned to the need to keep ammonia and nitrite levels at or near zero. In addition assume that you already know the importance that aeration plays in maintaining adequate dissolved oxygen for your fish to thrive. Most likely you even plan on partial water changes from time to time to remove dissolved organic compounds (DOCS) that have accumulated in your water, and you have made arrangements to remove any chlorine present in your water supply.

What else could you possibly need? Isn't this enough to ensure a watery paradise of an environment for your fishy friends and plants?

Not quite. You no doubt have heard the well circulated advice never to add harsh chemicals to your pond. This is generally good advice, but there are a few noteworthy exceptions. It is well to remember that watergarden ponds are NOT natural ponds. Natural ponds have a symbiotic relationship with water tables and springs and stream flows, and their bottoms are not simply receptacles for fish feces as are watergardens (This is why bottom drains are a good idea...Water gardens are more like great big aquariums than they are natural ponds). Consequently, we are faced with un-natural situation of our own making, all the while pretending that what we have wrought is natural. In short, it may be necessary to add chemicals to your pond in order to achieve the nirvana you desire for your fish and plants.

The first chemical you may wish to add to your pond is sodium chloride. This is salt. You will hear many pros and cons regarding use of salt. I believe the pros have the best argument and that a concentration of 1 part per thousand is helpful to your fish and marginally detrimental to your plants. See Salt in Ponds for a more in-depth discussion.

The next chemicals you may need to add to your pond are bicarbonate of soda and calcium carbonate. First, you must test your water for general hardness and for carbonate hardness. If these factors are not high enough, your pool may experience wide swings in PH (relative acidity to alkalinity) between day and night, due to the action of photosynthesis in your plants. Wide swings in PH can kill your fish. Thus, everything you do that can cause a change in your pond's PH must be done very slowly, if fish are already in it.

In order to monitor the general and carbonate hardness of your pond, you will need a test kit. I like the one put out by Aquarium Pharmaceuticals (Master Test Kit Product No 34). Carbonate hardness should be above 90 parts per million. Increase carbonate hardness by adding sodium bicarbonate (Bicarbonate of soda) at the rate of 1 cup per 500 gallons daily until the desired carbonate hardness is achieved. General hardness should be above 150 parts per million. Increase general hardness by adding calcium carbonate or by making "PH Pills" out of Paris, mixed with water and allowed to harden in plastic tubs {like small cool whip containers} and placing them in your biofilter. (See Dr Johnsons "PH PILL" at

These actions will raise the PH of your pond water. Remembering that the ideal PH is 7 to 7.2, you may wish to adjust it downward. Again, this must be done SLOWLY if fish are present. Adjustments of PH should not exceed .2 per day, therefore, if your PH is 8, and you want to lower it to 7.2, this must be done over three days. To lower your PH, add either WHITE vinegar or muriatic acid ( also available at Home Depot){Safety Note: muriatic acid is dangerous. Take care not to spill or slosh while pouring. Handle only out of doors. Wear rubber gloves, old clothing, and eye protection. have bucket of clean water nearby to flush if you spill any on you. KEEP AWAY FROM CHILDREN and store safely.} Start with 1 tablespoon (plastic) per 1000 gallons. Because your pool is now properly buffered with the addition of the calcium carbonate and sodium bicarbonate it may take some time before you see a change in the PH. Don't try to hurry it up, just keep adding the same amount day after day until you see a change. Re-check and re-adjust your general and carbonate hardness after achieving the PH you want, then re-adjust the PH. You will need to re-check these levels each time you do any water changes. [Caveat: Again, any downward adjustment of PH can be hard on your fish. As long as there is no measureable ammonia or nitrites in your pond, a high PH of even 8.5 will not harm your fish]

Potassium is another important chemical your pond may need. Purchase muriate of potash, and add a tablespoon per 1,000 gallons each month during the summer and you will see lush green growth in your water hyacinths and other water plants. There is also evidence that potassium helps fish growth as well.

The last area of concern is probably the most noticeable one: water clarity , or the lack of it. This is due to suspended particles in the water. They may be clay particles, silica, or algae. In dealing with water clarity, you may already have helped the situation if you are utilizing the PH "PILL" above. Adding calcium sulfate (Gypsum) may be the best water clarity treatment in your bag of tricks, This is because it not only aids in coagulating and precipitation suspended particles, but also aids in your pond's PH buffering capacity. see GYPSUM, for a more detailed discussion of gypsum.

Another clarifying agent you may wish to add to your growing chemical arsenal is aluminum sulfate. Commonly known as Alum, it is available at your grocery store. Use 1 teasponpoon per 1,000 gallons if your water is not sparkling clear. Your fish won't mind it at all, but any snails you have may decide to go elsewhere (not an altogether bad result, given their propensity to eat plants instead of algae and to clog pump intakes). See ALUM for a more detailed discussion of alum.

Well, there you have it. Perfect water. Happy fish, happy plants and happy ponder. For reference purposes, here are the measurable attributes and recommended levels.



Last modified on February 28, 2000

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