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Water Quality at the Aquarium

Posted on Apr 28, 2016 by in Animal Care


Taking care of the animals at the Greater Cleveland Aquarium means taking care of their homes. Sometimes that means cleaning the décor, and sometimes it means taking care of the water itself…this is where water quality testing comes in. I do most of the water quality testing here at the aquarium.  There are many interesting pieces of equipment (with fancy names) that go into testing, including a spectrophotometer, pH probe, refractometer, and titration kit.


We test for a number of things at different times. Nitrogen is one of the most frequent tests. The nitrogen cycle includes ammonia, nitrite, and nitrate. Bacteria convert the toxic ammonia from fish wastes to less toxic nitrite, and then to the much less toxic nitrate. We test all of these regularly, adding reagents that will react to the nitrogen, and using the spectrophotometer, a machine that reads the color change and converts it to a measure of ammonia, nitrite, or nitrate.

Blank ammonia test, sample ammonia test, sample nitrite test

Two more very important tests are pH and salinity. Evaporation can change the salinity of the water as the salt gets left behind in the smaller volume of water. When adding water back, it is important to know how much fresh and how much salt water to add to keep the salinity in the narrow range that is best for the animals. These are tested with the pH probe and refractometer directly.

pH probe                                                refractometer

Alkalinity is related to pH. It is a measure of the buffering capacity of the water; its ability to maintain a steady pH in the face of other changes. We measure this with a titration kit.

Alkalinity titration

Some animals have special needs, and their water gets additional tests. For example, elasmobranchs such as sharks and rays require iodine, so their water is tested for it. Corals and hard shelled invertebrates like snails require lots of calcium and magnesium to make their shells. These are tested ensure the water always has enough for them. These two tests also use titration methods.

A lot goes in to making sure our animals are healthy and happy. What many people don’t realize is that chemistry plays a large role here at the aquarium in addition to the manual labor and biology that takes place in every day operations. I am lucky enough to participate in these roles for work every day.