Not a theory, terrestrial based plant matter contains anti-nutritional matter, and is why their use in aquaculture has always been limited. 100+ years of science, and billions of dollars in research and peer reviewed studies. A bit more than just a theory.
I suppose I misspoke on the theory part. Still not sure I agree since nutrition can be sourced all kinds of ways, but I'm not an expert. I have heard of fillers from dairy products though. And there's the infamous corn starch fillers.
Nutrient dense pellets does not equate to hard pellets, it is used to describe pellets that are high in nutritional matter, and low in non nutrients. Water is a non nutrient. Fish with smaller mouths should be fed pellets that are small in diameter, and suited to their mouth size.
I was referring to the amount of pellets by volume only, thinking that any reduction in nutrition caused by soaking would be made up in amount. I feed unsoaked smaller pellets and soaked larger ones in combination, depending on the fish. Only two of my fish seem to like 'crunching' pellets.
I have kept and raised fancy goldfish, all fed nutrient dense pellets, with no issues. Gel based foods have been around for decades, Repashy didn't invent the concept. Again, water is a non nutrient, so if one feeds those kinds of foods they best feed off & on all day, or the fish will eventually become malnourished.
There is nothing new to pre-soaking pellets, people have been doing it for longer than I have been in the hobby, since late 1960's off and on. The main issue with pre-soaking pellets, is a large percentage of the water soluble vitamins can leach out. Another reason why I never recommend flake food, by their design they leach vitamins out at a very high rate, which begins the second they hit the water.
I realize gel food is old news, just thought of repashy first. A lot of people have their own recipes out there, some are pretty wild.
It's not that one can't presoak pellets, clearly they can, but typically there isn't a reason that one would need to pre-soak pellets fed to a flowerhorn, something that I have a bit of experience in as well.
I must admit I haven't heard of FHs getting them soaked but someone out there probably does.