I suspect that before the fish 'emulsion' can't sustain the plant the roots will fill the container and kill the fish.
If you search this forum for aquaponics, you'll find some decent discussions on it (as well as some less fruitful) as well as links to better sites.
from what I've read on those threads and/or sites, you need a lot more fish to provide ample emulsion for the plants. Also, some fish are better suited to surviving in water with high fertilizer concentrations. Typically, the discussions revolve around edible fish as aquaponics normally tries to capitalize on the dual food source perspective.
As advacodo grow into a tree, it may not be the ideal plant to experiment with aquaponics on. However, best of luck with it. At the very least, your son will get some nice action / consequence learning from the project.