Oh yeah in regard to the frozen shrimp, unless it was a large hard frozen piece with sharp edges it would likely do no damage. If this did somehow damage him internally, this would also take a while to take a toll, and there would be other indicators like just going of feeding for while.
Shrimp is high in thiaminase, so feeding as a sole diet, long term, will result in vitamin B1 deficiency. Here is an excerpt from my book that lists thiaminase containing seafoods:
Thiaminase
Thiaminase is an enzyme that metabolizes or breaks down thiamine (vitamin B1). In high enough concentrations in food, thiaminase will create thiamin deficient diets in fish. This is a common, yet serious problem with predatory fish that are fed feeder goldfish, as goldfish are very high in thiaminase. Lionfish, piranha and oscars cichlids were commonly fed all-goldfish diets by home aquarists. Health issues in their fish were then very common; fatty liver disease in lionfish, pica in piranha (where they eat each other to try to get more thiamin) and HLLE in oscars. Fresh seafoods known to be high in thiaminase can be supplemented with thiamin. Conversely, aquarists can avoid feeding fresh seafoods known to be high in thiaminase. The following is a partial list of seafoods that contain thiaminase:
Species high in thiaminase
Anchovy (Engraulis sp.)
Atlantic herring (Clupea harengus)
Capelin (Mallotus villosus)
Carp (Cyprinus carpio)
Clams (family Veneridae)
Goldfish (Carassius auratus)
Lobster (Homarus americanus)
Menhaden (Brevoortia spp.)
Minnows (Cyprinids)
Mussels (Mytilus spp.)
Rainbow smelt (Osmerus mordax)
Sardine (Harengula spp.)
Scallops (Pecten spp.)
Shrimp and prawns (various species)
Skipjack tuna (Katsuwonus pelamis)
White bass (Morone chrysops)
Yellowfin tuna (Neothunnus macropterus)
Species lower in thiaminase
Atlantic cod (Gadus morhua)
Atlantic hake (Merluccius bilinearis)
Atlantic halibut (Hippoglossus hippoglossus)
Atlantic mackerel (Scomber scombrus)
Atlantic salmon (Salmo salar)
Brown trout (Salmo trutta)
Catfish (Ictalurus and related spp)
Cisco (Coregonus spp.)
Coho salmon (Oncorhynchus kisutch)
Flounder / sole (Pleuronectes and related spp.)
Haddock (Melanogrammus aeglefinus)
Hake (Urophycis spp)
Lake trout (Salvelinus namaycush)
Mullet (Mugilidae spp)
Poecilids (Guppies, platies, mollies)
Pollock/Pollack (Pollachius spp.)
Rainbow trout (Oncorhynchus mykiss)
Tilapia (Oreochromis spp)
Worms (Lumbricus spp)
Jay