Thank you for raising this question, Kelly. After the initial set-up, the maintenance cost is actually very low. Basically, power for the pump and food for the fish. I ran some numbers to give you an idea:

For electric costs, let’s look at a 45 Watt submersible pump that moves 550 gallons per hour. For this example, we use an energy cost of $0.06/kWh but you can check your energy bill to find the number for your area.
45 Watts/1000 = 0.045 Watts per kWh, 0.045 Watts/kWh x $0.06 = $0.27/hour.

To run continuously, calculate the number of hours in a month and multiply by Watts/kWh:
24 hours x 30 days = 720 hours per month
0.045 Watts/kWh x 720 hours/month = 32.4 kWh per month.

To calculate cost per month, 32.4 kWh/month x $0.27/hour = $8.748/month. So for under $10 per month, you can run a 45 Watt submersible pump. This is probably less than the monthly cost of gas to get to and from the supermarket, let alone the actual cost of organic produce and fish.

Now if we look at fish food, it costs around $0.30-$0.60 for each pound of fish grown (1 pound of growth requires about 1.2-1.7 pounds of feed). So if you have 25 fingerlings growing about 1 pound per month, the cost would be roughly $7.50-$15.00 per month.

Can you think of any other recurring costs?