Can torts eat water hyacinth? I know my sliders eat them. I have them growing (exploding) in the pond and some in my Russians water dish. The Russians haven't touched them yet but I thought id make sure.
They are known to uptake heavy metals and are 90% water. Not much nutritive value there... As dry matter they have a high calcium concentration and a very favorable Ca to P ratio.
If you are able to get them from a reliable, uncontaminated water source, I wouldn't see a problem adding them to a varied diet. I considered them as a foodstuff at one time but due to my source (the canals) and the relatively low return, discounted them.