This is a question of ecosystem health.
I'd have no more concern eating salad greens from a floating raft than from a traditional garden if the
pond is healthy.
I'd have huge concerns about either if the pond or the garden soil were unhealthy.
Then again, I'm quick to agree with the flaring raft because I appreciate
aquaculture and aquaponics.
I think fish waste is excellent plant food and a far safer source of nitrogen than bags of chemical waste from a big box store.