I'm slightly new to aquaponics. I worked on an aquaponics farm for a couple semesters in college, not in too intense of a capacity. Mostly maintanance and monitoring. But I have my degree in soil science and when growing in soil a lot of nutrients tend to get over looked. I feel like there is most definitely this chance to happen, most specifically with silicon.
How to people ensure that enough silicon gets into their plants? I'm not an expert on fish or fish food, but I don't think that fish waste would accumulate a lot of silicon especially when their habitat is a closed system.
Also as far as calcium, what ratios are people getting with calcium vs NPK in their systems.
In media based systems with river rock or some other natural stone or perhaps even expanded slate or shale, the media may well provide enough silica. I'm not sure but I suspect that the coco coir used by some people for their seedlings may well help with silica (I know cutting down palm trees dulls saw blades due to the silica content of those plants.)
However, I do know people who really recommend using a potassium silicate product for pH and potassium supplement as part of the regular rotation especially for purely raft based systems. I can't say that I have ever done that but I'm not running any purely raft based systems. Perhaps adding silica might help my plants. The Lab and testing I've been doing lately doesn't test for silica levels so I really don't know. I might have to see if one of their testing options includes a silica test.