andrew.kantor@roanoke.com

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When is a fish like a canary? When it's one of the tiger barbs in Biological Monitoring Inc.'s Bio-Sensor - a machine that uses fish to make sure that drinking water is safe for humans.

The BMI system relies on two simple principles. First, that fish are sensitive to the water they're in. Very sensitive. Second, that every organism produces an electric field that can be monitored. That's why you can have an EKG without having an electrode in your heart.

"Fish generate a bioelectric field due to neuromuscular activity," explained David Gruber, the Blacksburg company's president. "We pick up that signal."

By monitoring that field second by second, the system can detect if it changes. If it does, that means something has changed in the water.

Those two principles are encapsulated, literally, in a box the size of a college-dorm refrigerator, with compartments for eight fish. Each compartment contains a sensor, and water is continuously pumped through these tiny homes. The fish swim while a computer keeps track of the electrical field they emit.

Obviously, one sample of water isn't identical to the next; there are small changes in minerals, pH and other factors. The fish's bioelectric field fluctuates as the water does, and a computer monitor displays readings from each of the fish. But, as Gruber explained, "if there was an industrial accident or sabotage, or a truck accident, or a farmer dumps a load of pesticide," the fish's reaction would be much stronger.

That kind of strong reaction would trigger an alarm in the system. (By default, at least six of the eight fish would need to be affected, although that can be changed by the user.) The Bio-Sensor would immediately take and store a water sample, then phone an alarm to two user-selected numbers. Once alerted, water authorities could run comprehensive tests on the water to determine what chemical or organism had entered the system.

Like those coal-mine canaries, the fish are not intended to provide a detailed analysis of the environment, just an initial warning. But because detailed water tests can be expensive, having the Bio-Sensor means communities can save money by only running them as needed.

Keeping it simple

Simplicity is the key to the Bio-Sensor. Except for some basic training on its use and maintenance, it's plug and play.

There's no adjustment necessary; the system calibrates itself in about an hour. Nor does it care what kind of fish are inside. "It develops its own baseline for each fish," Gruber said, although he recommends against using some, like catfish, that are pollution-tolerant.

"If there's a particular chemical you're worried about we can do the research" to choose a species, but in general he suggests that users simply go to a local aquarium store and buy some fish. "People are just trying to make this more complicated than it needs to be," he explained. Any small fish that can live in an aquarium will work.

The fish are even fed automatically (although the feeder needs to be kept filled).

"You've got to keep it simple," Gruber said, although he acknowledged that users may not trust a system that works so quietly in the background. So there are several indicators, as well as a fold-out computer monitor for the curious. "You've got to have blinking lights, so we have blinking lights," he explained.

Gruber also realizes that some users will want more control than "set it and forget it," so the system can be customized in a variety of ways. It can be calibrated to detect specific biological or chemical toxins, and the threshold for an alarm can be raised or lowered - a community could make it more sensitive during an Orange Alert, for example.

The Bio-Sensor can also integrate most other kinds of water monitors, beyond the fish. It comes with four such additional sensors: for temperature, dissolved oxygen, pH and conductivity, but different water authorities might, by law, have to test for other factors.

BMI has about 20 Bio-Sensors in service in cities including Los Angeles and Phoenix, and in countries including Australia, Namibia, Singapore and South Africa. The system costs between $35,000 and $40,000, and BMI offers a leasing option.

The Bio-Sensor may not be as sophisticated as more elaborate water tests, but, as Gruber put it, "If there's something toxic in the water, the system detects it."