Here's the type of food I have been feeding the fish for years. This brand is low-glycemic formula puppy small breed for the smaller fish. You get a big bag for 16.99 that's super fresh, and just made, and made in Alberta. I feed the large five pound koi the larger kibble with no grains at all. It's very high quality dog food that has botanicals, farm fresh eggs, salmon, northern white fish, bison, etc. The large bag costs me about 75 dollars. The puppies don't eat as much cause without the grain, they are fuller longer and don't tend put on weight. Feed to the fish they love it! The very large koi will come half out of the water to eat it out of my hand! I think that they weigh at least five or six pounds each and they are VERY strong! They try to rip the fingers off my hand! I would go broke trying to feed them fish food that I don't believe to be as fresh or wholesome as this brand of puppy food. I never buy the seven year old puppies adult food either cause they would just eat twice as much to get the same full effect. I don't do low saturated fat so I would not feed the dogs low fat, cause I don't believe the low fat crap is better. I think people who eat low fat crave sugar and carbs to fill the void, I see this all the time with my friends.
Should you choose to feed your fish dog food as many others that I know do, you can find similar types of dog food made in your state or province that would also be just as good. I have never had water quality issues feeding this to my fish, they gobble it up very quickly and there is never any left over, unlike the fish food! I also have very large sedges that clean the pond very well, and I also have very good water movement and filtration. The fish also grow very big eating this, and they have good color as well, and have not seen any sick or dying goldfish or koi, so it has to be good! (Except for that tropical Tin Foil Barb, that I put in the pond when the water was still too cold, early this spring)