Ok. Thank you. I was mainly worried that I was feeding them the wrong thing. I also noticed that the neons were struggling quite a bit with the crisps. Maybe I'll switch back to flakes.
Thank you very much for your detailed answer! Do I have fish that would benefit from a plant-based diet? I was told by a source that golden gouramis cannot tolerate red mosquito larvae. Is that true? The dead gourami was also slightly fat after death.In terms of quantity...don't ask us, ask the fish. If they completely eat all the food you offer and still seem ready for more, then the quantity is good. If there's still food drifting around and the fish have lost interest in it, reduce quantities. I think your quantities are good, far better than most aquarists who tend to obsessively overfeed.
I am a firm believer in offering a variety of different foods. If fish are fed a constant diet of the same commercial food...even if it is nutritionally complete and perfect...you may run up against a problem if for some reason you can no longer obtain that product, since the fish may not readily accept another, at least not at first. This is more of a problem for the aquarist than for the fish; in almost all cases they will begin to eat something new after a few days or even weeks of fasting, but most aquarists will crack under the strain of watching that.
I also think that it improves the fish's quality of life to have a variety of foods offered. In fact, I rarely feed the same food twice in a row, and my fish seem to be more enthusiastic at feeding time. I use the same strategy my mother used on me. I was given two choices at every meal; take it or leave it.I didn't starve.
Frozen foods are a big part of my feeding regimen. When I feed I will thaw the portion of food in a glass of warm water, allow it to settle to the bottom, and then pour off the upper 90% of water and dispose of it rather than just dumping the chunk of ice into the tank. When frozen foods thaw they release a large quantity of juice, blood and other organic matter into the water. This stuff cannot be utilized by the fish but it certainly can and does degrade water quality, so I want to minimize it in the tank. And while much of the nutrition in the food is lost during the freezing/thawing process, it isn't accurate to say that frozen foods have no nutritional value. They aren't as nutritious as the fresh live version, but there is still much solid nutritional matter in them and they are clean and parasite-free. I also use a fair bit of freeze-dried foods, always pre-soaking them so they can absorb water and re-hydrate before being eaten.
I like the crisps as I feel I am getting more food for my money with them. Flake foods are almost entirely air; a pinch of flakes on the surface looks like more than it is, as the flakes are microscopically thin and take up a lot of area. But for very small fish like your tetras, flakes are easily eaten compared to crisps, pellets, etc. Flakes are also very easy to grind down either between finger tips or with a spoon into smaller chunks for even the smallest of fry.
I'm also an obsessive label reader. It doesn't take a doctorate in nutritional science to quickly see that a food whose main ingredients are natural aquatic items like fish, shrimp, spirulina, etc. is going to be better than something in which the first ingredients are a couple different types of "something-or-other meal". That's code for "absolute garbage that we can't otherwise use". Fish in nature don't eat corn, soy, ground-up feathers or many of the other things that are in some commercial foods...so fish in aquariums shouldn't either.
Protein is nice, but...the source of the protein is also important. There are also some largely herbivorous fish that actually do better with lower protein foods that mimic their natural diets of low-protein vegetation, and may experience problems if fed too much high-protein carnivore-type diets.