The reason behind using SW food with SW fauna is its components.
A sal****er fish needs proteins and other nutrients in a specific ratio.
They evolved obtaining those nutrients in a certain ratio that is default in
SW food.
Is like feeding Eucalyptus leafs to a Panda and Bamboo leafs to a Koala.
Each leaf contains the necessary nutrients to feed either animal; but...
Pandas evolved a digestive system specific to Bamboo leafs and this system
is waiting for the ratio of nutrients found only in this leafs.
Same goes with Koalas, they only feed in Eucalyptus leafs.
Will Koalas survive in a diet of processed and compressed Bamboo leafs?
probably but will be subject to malnutrition. Same with Pandas.
I know, these examples are a little exaggeration but serve to explain the
importance of feeding the proper food to our species.

"Pszemol" wrote in message
...
"Gill Passman" wrote in message
...
Absolutely so here is the dilemma....on one hand it is good to feed FW
stuff from SW and SW good from FW from a pathogen and disease
prevention point of view...but on the other hand the nutritional
requirements differ....

There is no dilema!
Deep frozen stuff you buy for your fish
is pathogen free and safe to feed to your pets...
Unless you feed live foods you should be perfectly fine.
The best food for marine animals is marine in origin.