Diversity, mainly. Grow many different classes of plants, not just food products. Start a nearby beehive and include plants with large numbers of tiny flowers.

Diversity, mainly. Grow many different classes of plants, not just food products. Start a nearby beehive and include plants with large numbers of tiny flowers. Include crayfish and other filter-feeders with the fish. Keep a few trees (cactuses?) around to provide bird habitat. Basically, yeah, artificialness is a liability, and it should be minimized intelligently. Not by imitating a jungle, that is impossible, but by being highly aware of the local microbiomes and gently supporting beneficial negative feedback loops. Make friends with a biologist. As for the micro nutrients, this is what the fish and insect side of the system takes care of. If there is a deficiency, try to make it up through fish feed, not by directly feeding the plants. Fish hate concentrated fertilizers. Maintaining a barrel of "compost tea" is also an option, but it should be filtered through lots of grow media before the fish get it. If you are really really brave, you might choose to experiment with a graywater system, but there is huge potential for problems like parasites and bacterial (i.e. E-coli) explosions.