Pond troubleshooting is something all pondkeepers must do. Things can go wrong in our ponds and we must know what to look for, so we can keep the problem from becoming a disaster.
Several years ago, I was called to care for a pond that filled my customer's front yard. He had built it with concrete, making any pond difficult to keep balanced. Concrete can leach lime if not sealed properly. He could not keep water lilies or fish alive. What was wrong? I could see the pond was about a foot deep. Problem number one was found. A pond must be at least 18" deep to keep both water lilies and fish happy. The water was getting too hot for fish to survive, so problem number two was found.
My customer built a second pond attached to the first one. It was 18" deep, and still concrete. The ponds were connected, so the fish and the water lilies could both live in the deeper part of the pond. We planted parrots' feather in the shallow pond to keep the water shaded and cooler. Over the years the parrots' feather grew so large, it took two men to drag it out and cut it back when the pond got its annual cleanout.
We thought we had the problems solved, but we were wrong. I had a motivated client. He loved his pond and did much research on pondkeeping, so we could try to figure out the problems together.
Within a year, the fish began to get sick, the submerged vegetation started to turn yellow and lose all its leaves. Now what was wrong. My first instinct was to check the pH. It's easy, but rarely the problem. pH usually fixes itself in a balanced pond and this one was balanced. My client did not feed his fish, so we did not have excess fish food or organic waste to deal with. Most people, if they feed their fish, feed them too much and much of it falls to the bottom of the pond, where it decomposes and fouls the water. Even if the fish do eat the food, they produce so much waste, that it fouls the water. You can always tell if people feed their fish even if they say they don't. If you walk to the edge of the pond, the fish come to the top, racing toward you smacking their little mouths waiting for their treats. All the while, the pondkeeper is protesting, saying he does not feed his fish. Then he gets busted by his own fish.
But that was not a problem with this pond.
Neither was pH. Excess ammonia was not a problem, nor were nitrates or nitrates. All of these things must be dealt with if fish are fed.
So why was the submerged vegetation dying, the water clouding up and the fish dying, but not all at once. My first hunch is always that chemicals from somewhere are getting into the water. Check to make sure water is not running off from surrounding streets, insecticides or pesticides being sprayed by the gardener, the neighbors' gardener or the city. Make sure there is no rain running off the roof into the pond. Nope, not at this house. Check with the neighbors to see if anyone is scraping paint off their houses and microscopic particles are drifting into the pond.
By this time, I have been working on this pond for several weeks being a real pond detective.
As a last resort, I pumped all the water out of the pond and started over. Within a week the pond was cloudy and foul again. What was the problem?
The client had household staff. He also had an entry just outside the front door. It was about 8 feet wide and 40 feet long. It was the only way people used to enter and exit the house. I asked all the staff about their shoes. Did they have new ones? Did someone drop something in the pond? Did the nanny let the kids put things in the pond? No to all questions.
Finally, I asked the right question. I found that one of the staff members had decided the patio entry needed to be cleaned at least twice weekly. She sprayed it with floor cleaner, scrubbed it and then hosed it off.....right into the pond.
After being assured she was not going to be fired, I asked the staff member if it was OK to leave the patio a bit on the dirty side. She agreed. The pond recovered. The anacharis was replaced as were the fish. The crisis was over. It took about 2 months and 10 visits to find the problem and fix it.
There is always a reason that ponds get foul and fish and plants die. Most of the time the reason is relatively easy to find and fix. Occasionally we must play detective and take much longer to find out what is happening. Keep on looking for your pond problem. You will find it. After that, fixing the problem is easy.