There was a time when the majority of carp anglers used trout pellets in one way or another and the choice of pellets was quite limited compared to today. Pellets were usually ground up and made into boilies and paste baits. Pellets were also used as free baits but most often simply introduced with no additional treatments or adaptations to make them far more effective at making fish feed.
The thing to think about is that pellets such as trout pellets, salmon pellets and halibut pellets are designed to put weight on farmed fish for maximum profit. They are not optimised to make fish feed most of all. They are optimised to ensure the most feed gets efficiently biologically converted so the farmer has healthy fast growing fish to profit most from. Feed triggering efficiency is not the main aim at all! This point is a massive one to remember every time you use any pellets not designed specifically for carp fishing! This point means that you must treat pellets to maximise their feed triggering impacts!
You might well assume that for instance that halibut pellets are ideal for carp however they are certainly not ideal for health and certainly not optimised for maximum numbers of bites. These pellets are designed for fish with a higher protein requirement and a higher energy requirement which additionally means that such sea fish and salmonids such as salmon and trout have a higher oil content than carp require as carp metabolism is lower over all that these other fish.
Halibut pellets are high oil and used in volumes by numbers of anglers all the time on lakes is bad new for carp as this imbalances their ability to generate energy and burn off stored fats and glycogen in and around the major organs, and affects blood triglycerides and cholesterol in the body detrimentally. High oil impacts produce vitamin E deficiency and as this is a very potent antioxidant this reduces the immune system and other roles and functions in carp.
Fatty liver is just one symptom of excessive salmonids and halibut pellet use by the herds of anglers using these in spod and PVA product mixes and as other forms of free baits. It is insane how many carp have enlarged livers that form a bulge in their side which so many anglers simply ignore not realising they are harming fish health by using such pellets! The impacts all add up and in fact slow down the fishing especially in the later autumn, the winter and spring because the excessive and ignorant use of pellets by the masses simply means so much oil is converted and stored for vital energy, that very little feeding is required outside of optimum water temperatures for carp feeding!