Canaries in the Pool

Do you recall stories about coal miners or gold miners of old taking caged canaries into their underground tunnels to detect poisonous gas? The poor little birds are so sensitive, they croak at the first wisp of dangerous air, thus protecting the men -presumed somehow more valuable than the bird- from harm. Well the science and art of pool-water care not to be outdone, we, at least once, used "canary fish" for a similar purpose.

Curiously, it was a researcher at a world-famous aquarium that did the work, yet we pool folks can gain immensely from the amazing inference revealed... ‘Seems knowledge of the distribution of ammonia compounds throughout a body of water became important to the keepers of so many valuable, exotic fish. They were first attempting to create a measure of "sanitation" of the aquarium in order to eliminate or suppress a troublesome, parasitic fish pathogen that had recently gained a foothold. The ichthyologist first considered copper, quickly discarding the idea since the poisonous residual would persist. Chlorine, also poisonous to gilled fish, might work as it quickly dissipates or is otherwise consumed. Any valuable or especially sensitive fish removed for the process could then be returned to the tank.

Certain that any low-level chlorine residual introduced would quickly compound into chloramine, they pondered the rate of such development and the location (strata) within the body of water where such amine would first show up. Towards this end, trace amounts of chlorine would be added, during which time all but the toughest fish were transferred to a holding tank.

Now for the canaries. Our innovative researcher reasoned that samples grabbed at various depths and locations would be extremely difficult to analyze and compare, as ammonia compounds and other chloro-unmentionables could change or disappear on the way to the lab. Such tiny residuals expected would be hard to determine with accuracy even at tankside, using standard, field-test gear. He therefore decided to go empirical, right to the consequence of concern – the death of a "control fish" would indicate an unacceptable level of amines.

Here’s where the animal-rights folks may wish to stop reading. Ten very small, very sensitive-to-chloramine and very common (could we guess expendable?) little fish, sort of the salt-water equivalent of a feeder goldfish, were selected for uniformity and vitality. They were then individually caged in small wire-mesh boxes which had been attached to a 12-foot pole about a foot apart. (Details escape the writer, but one assumes the pole was horizontal, just underwater in an adjacent tank, during this careful operation.) There these unwilling volunteers for science waited, oblivious of their fate.

The water in the main aquarium had been treated earlier in the day with about three tenths of a part-per-million sodium hypochlorite. This was enough of a chlorine dose, according to earlier tests in a small tank, to eliminate the offending parasites. Enough time was afforded to allow an even distribution and some measure of equilibrium in the development of the presumably dangerous "products of incomplete oxidation" – the ammonia compounds of chlorine.

The moment of truth arrived. The victims were mercilessly exposed. The condominium pole with its dozen residents was immersed and affixed vertically in the main aquarium, and the hands of a stopwatch were set in motion. The test fish were uniformly distributed, vertically, in the deepest part of the tank, with the top apartment just under the water’s surface. They (the researchers and the fish) waited.

The penthouse was not the place to be that day. Within ten minutes the fish in the top cage gasped its last, quickly rolling belly up. About thirty minutes later, the next volunteer, just over one foot down, began showing signs of distress. It quietly transitioned to gillfish heaven in just a few minutes more.

Now the third fish down lasted, we are told, over three hours, finally making his sacrifice with dignity. The fourth, however, and the fifth... right to number 12 near the bottom, remained all the next day, earning their right to be – like the White-House turkey on Thanksgiving day – freed forever. They never succumbed, because virtually all the ammonia products were near the surface! Like the proverbial canary, the one who survives provides just as critical an indicator as another who gives his all.

Are you beginning to catch the value in this bizarre little exercise in empirical science? We pool guys can conclude that pool-water chloramine, when it exists, is much more prevalent at or near the surface, and nearly non-existent near the bottom!

It makes more sense now – that caution we've heard so often: A high rate of air exchange at the air/water interface is critically important when striving to achieve breakpoint. No wonder superchlorination works in deep pools as well as shallow, while no bubbles of nitrogen nor who-knows-what else are ever seen rising from the deeper bottom as the ammonia compounds give up their gaseous components. It all happens at the top; doesn't need to happen down deep. Wow. Superchlorination is truly a surface phenomenon!

Finally it has become apparent (the canary fish showed us) how breakpoint can really happen in a matter of hours, even though Doctors Gage and Bidwell (PrP #13) tell us it takes many times that amount of time for even a single thorough circulation of it all to occur.

Is it molecular weight? Is it partial-pressure ratios? Is it magic? We may never find out why chloramine rises. But those fish lived down there deep; that we do know. And we understand better where, if not how, the breakpoint activity takes place.

~kw

(Superchlorination, the voodoo part of pool-water care, has been discussed at length in PrPs # 8,9,10,11 and 13!)