Tilapia would have been ideal for the aquaponics system, but Montana regulations do not permit transportation of those species. Some aquaponics enthusiasts around here think that is crazy because tilapia live in much warmer waters. However, they can be very invasive where they do show up, and with weather patterns changing, why not be cautious?

As mentioned previously, aquaponics systems do require some intelligent and informed maintenance on the part of the gardener. We found that for our situation, the best plants to grow were basil and chard. We ran into a few issues over the course of time we have been in operation. Below is a diagram of these issues and what we did to manage them:

Problem	Solution
Hard water	Water in the Missoula area has a lot of minerals that cause the pH to be higher than the pH where plants can uptake most nutrients. Normally, the best thing to do in this situation is use a reverse osmosis machine to remove the buffering salts from solution but the UMDS did not have the funding for a reverse osmosis machine. Another solution we have been using for our home demo system is to dilute the hard tap water with rainwater. The university is interested in implementing rainwater catchment, but it was not available to us quite yet. So in place of a better solution, we have been limping along measuring and adjusting the pH, and carefully adding small amounts of muriatic acid to bring the pH down to a level where plants can absorb the nutrients in the water. It is important to do this slowly because too much acid can kill the probiotic bacteria responsible for making nutrients available to plants. We really struggled because hard water salts were precipitated on the edges of the mixing tank and when we added the acid they would dissolve into the solution, raising the pH again. Buffers are a b*tch.
Cholorosis	Because of the hard water, the plants had difficulty absorbing many nutrients. This made them look yellow, aka “chlorotic.” The pattern of yellowing and dying plant tissues can be informative about the particular nutrient that the plants are struggling to obtain. We experimented with giving them supplementary chelated iron and zinc, and potassium. They reacted favorably to these additions, but some of the nutrients we added probably were precipitating out because the pH was still too high for them to be in high concentration in the water solution.
Dripping	The media towers that the plants grow from are a really great product, but they do tend to leak on the floor, which is a safety hazard in a public space. This was easily remedied by leaning the towers at a slight angle and pruning the lower leaves on the plants when they got really bushy.
Too much nitrogen	Because of the hard water issues, nitrogen uptake was slow for a period of time. The high nitrate concentration in the water was stressful on the fish and some of them died. We changed the water to dilute the nitrogen buildup, but the water that we added needed to be pH adjusted first.
Aphids	Aphids appeared because outdoor plants were transplanted into the indoor system. This is a common occurrence in controlled environment systems; something that was kept at low levels in a complex garden ecosystem becomes a pest when brought into the more simplified controlled environment ecosystem. In our home demo system, we introduced ladybugs to bring down aphid numbers, but because this was in the school cafeteria that did not seem like a reasonable solution. We were not about to have a bunch of ladybugs flying around the cafeteria, laying their eggs, and dying on people’s california rolls. Currently the garden managers are hand squishing the aphids and this works alright for now.

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