As we know by now Gallus and Silverstream are the only predators in the student six and probably in the school too.
I would love to hear your opinions about how they can deal with it and what kind of problems could coming from this, so open widely your fantasy.

I'm pretty sure about that at some point in their school life Gallus and even Silverstrim would start hunting for animals. I believe they could get in trouble in the Everfreeforest either because they would accidentally hunt down one of Fluttershy's creatures or simply lost in the forest or something would attack them.

Since Silverstrim spent most of her life under the sea/ocean I'm sure she loves fish and other sea fruits but I don't close it out that she would eat other meats too.

Maybe they eat pigs? Ham/bacon/hotdogs? Pigs aren't really shown to be sentient. I'm sure Fluttershy would be concerned, but one of her friends is a bear, so I'm sure she understands that some animals need to hunt and not all are vegetarians. As for Silverstream, nothing is stopping her from going fishing in the lakes/ponds in Ponyville. She could be enjoying a fish dinner every night, same with Gallus. He might like fish too. He's part bird. Birds enjoy fish. Gallus could also eat insects.

Dragons eat gems, but I can also imagine Smolder being more willing to try meat instead of 'bland pony stuff'. Same with Ocellus. Changelings never had to actually eat food FOOD until they evolved into colored changelings. They just fed off love. I can't see Ocellus being against meat, since her former food source was more or less the life energy of a creature. Drained of love, a pony or creature is probably nothing but full of hatred and exactly like Chrysalis, so that was a bad thing. I can see Thorax pushing for a vegetarian diet, but maybe the other changelings don't care as much, since they'd always been forced to hunt for 'food' in the past. Pharynx saying the only thing he takes from Trixie and Starlight is 'breakfast' implies he didn't care where his meals came from.

Considering the sort of foods seen served and the reference to some sort of fish oil drink in "Surf And/or Turf," it seems the hippogriffs are most likely omnivorous. So I absolutely believe Silverstream will eat fish if offered, but her diet doesn't likely necessitate it, so I also think she wouldn't have to eat fish exclusively.

Therefore, I figure she alternates between seafood she gets herself and whatever pony foods the school cafeteria might be serving at her fancy, as I see no reason why she can't eat most staple pony dishes too, and Silverstream's all about trying new things anyway.

I highly doubt the show will ever go into detail about this itself, though, for a number of reasons but mostly because it is still a kid's show, and it'd be hard to bring up these subjects without breaking this standard its set for itself. At most, any indications of diet would probably be conveyed through the same way "Surf And/or Turf" did it: faint hints hidden in the background. But likely never an outright acknowledgement.

Fish seems to be available, Shy's been feeding fish to some of her animals since season 1.