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In the News: Tails of Marin

By Monica Norcia

Brush up on pond fish maintenance

Ask any pond owner and he'll tell you: Maintaining your pond is the key to happy and healthy fish. And now that the weather is warmer, it's time to start paying even more attention.

Seven years ago, my husband and I bought a home in Santa Venetia and inherited a school of koi and shubunkin (Chinese goldfish) housed in a funky, blue Jacuzzi. I didn't know anything about these beauties, but with each season change, I learned fast and, alas, sometimes the hard way.

Lesson No. 1: When in doubt, do a water change and don't forget the dechlorinator. When the weather is cold, fish hibernate and pond bacteria, both good and bad, can't thrive. However, as the pond temperature rises - above 60 degrees - bacteria multiply. Unfortunately, fishes' immune systems don't really kick in until the water is around 72, so until then, they're more susceptible to parasites and illness.

Partial water changes every seven to 10 days help keep your water chemistry stable.

Lesson No. 2: Now is a good time to clean old leaves and organic matter that have accumulated at the bottom of the pond. We finally built a gorgeous double pond with a waterfall for our finny friends and we lined it with large stones. Mistake. The stones trapped organic matter and turned it into a goopy black hazard. We had the stones taken out and the fish are now happy - and procreating!

Lesson No. 3: Invest in a good water chemistry kit, available at many pet stores. The liquid kits are better than the tablet form, according to some fish experts, and I find them easier and faster to use. You'll be testing for ammonia, which increases in the pond from the fishes' waste and should be at no more than .25 parts per million (no ammonia at all is preferable), nitrites, which should be less than .25 ppm, and nitrates, which should be less than 20 ppm. Regarding pH, an acidic pH can burn a fish's body and open it up to parasites.

Interestingly, our pond pH has always been about 8.6 and I tried different pH products to get it down to the recommended 7.6, even though the fish did not seem stressed by the alkalinity. Finally, I tested the tap water and found that, lo and behold, it was 8.2. There doesn't seem to be a consensus about what constitutes a high pH as there is for a low pH, but I've decided to listen to Dr. Erik Johnson of Koivet.com and one of the few fish doctors in the nation, who says that in areas of "hard water," it becomes even more important to keep your ammonia, nitrite and nitrate levels non-existent.

Lesson No. 4: Make sure that you have a good filtration system with UV powerful enough for your pond size and fish family. The filter intake should be at one end of the pond and the outflow at the other so you circulate the whole pond. Also, a good waterfall or strong bubbler is essential for oxygen distribution. (Your fish will let you know when they don't have enough oxygen by gasping at the surface.)

Lesson No. 5: A dash of salt cures many ills and keeps the fishes' gills efficient. I've decided to keep the pond salted year-round at .15 percent salt levels, even higher in summer. You can get bags of extra coarse salt at Safeway for about $3. Grab an old pillowcase, fill it with salt and hang it in the pond, measuring the salt levels with a trusty salt meter. Never pour salt directly into a pond as it can burn the fish.

And finally, hard as it is for most of us, try not to overfeed or overcrowd the critters. The increased waste wreaks havoc on the chemistry.

Monica Norcia, a fish hobbyist, is a cat behavior evaluator at the Marin Humane Society.