I'm pretty much with Tristan on this one in that food designed for a
certain animal is what the animal/creature should be being fed....yes,
my cat will eat the dog food, the dog will eat the cat food, the cat
will eat the fish food (but a bit cost prohibitive to feed a cat a
couple of cartons of marine flakes twice a day at around £7 a tub - but
useful for hoovering up spillages)....the dog will eat the food I give
my guinea pig and rabbit, the guinea pig and rabbit would eat the wild
bird food I put out - the cat would eat most of whatever is on offer but
I rather fancy the cat would prefer to eat the birds, the guinea pig and
rabbit - lol......haven't tried the fish on the diets of the mammals but
I'm pretty sure they would take it....and I am also pretty sure (with
the exception of giving meat the herbivores) that everyone would put on
weight and grow with whatever mixed up diet I care to give them....but
none would be healthy long term.....

Now it may well be true that one person has success in producing fat,
big fish by feeding them cat/dog food.....but equally most of us in the
Western World have had success in producing big, fat children by feeding
them an inappropriate diet....if we argue that the diets are
inappropriate for the children perhaps it should also be considered that
certain diets are inappropriate for our pets for the same reason.....

Now if the motivation is to get good bucks for fat, large but
potentially unhealthy fish then I guess that this is something we see
all the time in the fish trade...but it doesn't make it right.....

Now, when it comes to fish food.....expensive does not equal
good.....equally cheap doesn't equal the equivalent to other available
foods.....personally I've tried a number of foods (of varying price
tags) for my tank fish.....the conclusion has actually been that the
mid-range food suits better.....but not really because of how the fish
grow, colour etc. etc....but because of the impact on the water
quality......cheap foods contain a lot of bulk that eventually pollutes
the water with nitrates and phosphates, higher priced foods contain a
lot of protein (IME) which equally pollute the water with that rather
nasty oily skim on the surface (I dread to think what a high protein
cat/dog diet does - as afterall cat and dog food is designed to satisfy
the needs of carnivores).....the key is to find the food that suits you,
your environment and your fish.....Fish food suited to the fish is the
starting point....experimentation with it to get the desired results and
maintain the health of your fish is the goal.....feeding food not
designed for the animal in question is a non-starter....

Gill (getting off soap box for an hour or two)