The LSSU Aquaculture club has been operating three aquaponics systems for approximately four years, one with yellow perch, another with Atlantic salmon, and our largest system with koi fish. Our water is sourced from Lake Superior, so the source water has very few ions, and is aged before entering the systems. After several sudden mortality events, we have continuously monitored the water quality of our system, using API freshwater test kits and real time Wi-Fi enabled digital water meters that allows us to monitor the water remotely. In general, water parameters appear to be optimal with the exception of slight variation of pH and ammonia levels.
Our analytical chemistry professors offered to run water samples using their Inductively Coupled Plasma Mass Spectrometry (ICP-MS) equipment, and discovered high levels of metal ions at least an order of magnitude higher that the source water. Water samples were collected regularly to see if the metals were accumulating from the food or other sources of contaminants such as condensation from overhead pipes. We suspect copper levels may be elevated due to copper pipes, but we later analyzed samples of our fish food, which showed high levels of metals.
We encourage the use of closed loop systems to conserve water, but realize the potential for increased concentrations of metal ions, and so are interested in finding indicators of high metal levels before the fish show signs of distress. Currently we are monitoring the pH and note that over time, the pH drops if no water is replaced. If the pH drops significantly, we are doing @20% water changes which brings the pH back to optimal levels. We are currently monitoring the pH and conductivity, while taking water samples for ICP-MS analysis to see which parameters can be used as an indicator of potential increases in metal ion concentrations.
We are still not sure of the effects of high metal ion concentrations on the quality of life for the fish or the plants. We plan to examine the tissues of frozen fish mortalities and plants growing in the system for traces of heavy metals using ICP-MS and Micro XRF spectrometer.