The Mystery of the Stolen Fish Meds

by | Feb 3, 2022 | Aquaculture | 0 comments

Before being put on display, new animals arriving at public aquariums have to go through a quarantine process. This allows the curatorial staff to observe and treat the newcomers for any potential risks to the resident animals. But last year at Shedd Aquarium, their quarantine protocol, involving chloroquine phosphate, just didn’t seem to be working. After months of confusion, microbiologists were brought in to solve the mystery.

What was happening?

Aquarists would pour in the required amount to dose the tank and then take measurements to monitor the concentration. What they found was that the concentration was a lot lower than they had expected, “to the point where it wouldn’t work anymore”, says Northwestern University’s Erica Hartmann. The medicine was disappearing!

So who stole the meds?

Aquarists collected water samples and swab samples from the sides and pipes of the tanks and took them to the lab. 754 different microbes were found! By studying these microbes, they found the culprit. “Carbon, nitrogen, oxygen and phosphorous are basic necessities that everything needs in order to live,” said Hartmann. “In this case, it looks like the microbes were using the medicine as a source of nitrogen.”

What to do?

They couldn’t find exactly which microbe was doing the damage, but they did know where the nitrogen was disappearing – the outlet pipes. The solution? Flushing the tank with new water was not enough, the pipes needed to be scrubbed or replaced in order to prevent the chloroquine from disappearing.  Switching between fresh and salt water regularly in the future may also do the trick, as microbes are typically sensitive to one or the other.

Goes to show that there’s always more to learn about our aquarium systems! 🙂

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  • Heidi dM

    Heidi is a Marine Biologist who has been working in the public aquarium industry as an aquarist and now as a consultant specialising in husbandry, interpretation and staff training. She has also written a series of children's books about the aquarium and fish world called "Abby's Aquarium Adventures".


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