Cost of water changes vs chemical additives

Bingo, the lights are on and somebody is home!!!! I just came to major realization while chatting with my friend Chuck Jones of Wet Pets (KOI Farm in Dahlonega GA). Water changes are the only method for removing harmful bacterias and even blooming algae from your pond. All ponds have some nasty bugs in them. Chuck indicated that everyone he talks to is looking for that magical chemical you can dump in the pond to kill all the stuff we do not want, rather than going with a simple water change and regular cleaning of filters to remove detritus where anaerobic bacteria can build up.

So lets look at cost of Water Change vs Chemicals:

5000 gallons/month (166.7 gallons/day) is roughly 2.5 times my total pond volume. In my local municipality the cost of 5000 gallons of water/month via my irrigation line is $30.17. 990 gallons (33 gallons per day) is a flat rate of $12 + .00453 per gallon for the remaining 4010 gallons (134 gallons/day) is $18.17. I pay the $12 whether I use water or not. 167 gallons per day is about 3.7 inches deep of water in my main pond. I lose about 1″ per day from evaporation, leaks, splashout, and plant respiration. UPDATE – I finally found the leak in my pipes so I now only lose less than 1/4 inch (10 gallons) per day. Filter cleanings are about 200 Gallons per week of water lost.

Regularly used Chemicals
Algaefix – $9.99 small bottle
Melafix (anti bacterial) – $35.99 64oz bottle
Pond Clear (Flocculant) – $14.99
Total: $60.97
Note: you may not add all these chemicals every month so can be about the same when applying over months.

Pros/Cons of water change vs Chemical
– Water cost is about the same or lower than constantly applying chemicals to fight algae, floating debris, and bacteria.
– Water change removes the bacteria stored in settlement chambers and filters.
– Chemicals may not kill bacteria and bacteria may become resistant.
– Water changes reduces stress on nitrifying bacteria, chemicals may kill beneficial bacteria in the filter.
– Chemicals may cloud the water temporarily, water change clears water after particles settle
– New water added still requires a chlorine remover like sodium thisulfate or other products so would have to add in cost of those.
– Algaefix does work on string algae, so won’t completely rule out its use.
– Most flocculants add stress to the bio filter since the settled debris will be transferred to the filter.
– Improved fish health from good clean water will lead to less medication purchases. Unknown is the long term affect on fish with chemical additives.
– Water changes require a waste area to dump the water. Some people claim the dirty pond water is good for garden plants.
– Chemicals will be diluted when new water is added thus lowering their effectiveness. Or worse they may concentrate if evaporation occurs rapidly which may overdose for fish.
– Water changes and filter cleaning in winter may not be much fun. A good system design will help. Fewer chemicals may be needed in winter months.
– Water changes can take up to a couple hours/week. Adding chemicals is quick, but may not be affective right away. I always worry about the fish and check the pond every few hours after adding chemicals.
– Cost of water and water quality may vary greatly by geographic region. Rural pond owners may have to pre-filter water sources.

I am sure there is more to consider, so if you have any thoughts please post a comment.

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