I feed the dennerle 5in1 mix, ie you get 5 small sachets of 5 different foods, and as JoJo has mentioned I smash them with a hammer (best to do this before you open the packets) and mix in a tin or old ammonia strip snap top container. I also use the chi ebi same as Jojo, supposed to be good for babies/juveniles etc. I would think anything by the main shrimp specialists is going to be good, but would use several different ones alternating, or mixed, including something powdery for shrimplets, plenty of variety. I use an old shrimp lolly stick to put the food in the tank by wetting about a mm at the end, then dipping it into the food, knocking off excess back into the tin then swoosh it in the tank. I also use the beta glucan as JoJo but that is additionally, as food for the bacteria more than the shrimp (but again less than recommended by the makers). Every food I use a lot less of than the manufacturers recommend. In fact I don't really understand how the little food I put in supports the 100+ shrimps, but it seems to work so I won't mess with it. I do once a day feed but thats because I have too many bloody shrimps.............. luckily it is winter here so they have stopped breeding for now so I am having a nice break from having to cull some.
On saturdays I give them ORGANIC spinach leaves which the swarm too, so I usually use that as an opportunity to count them, it is really easy to use but must be 'organic':
https://skfaquatics.com/forum/forums/topic/14035-spinach-fresh-or-frozen/
On sunday I treat them to a shrimp lolly which they love and swarm over. I give them 1 lolly which is supposed to be for 30 shrimps but I have over 100, so again a lot less than the manufacturers recommend.
https://skfaquatics.com/forum/forums/topic/14030-shrimp-lollies/
My mentality for feeding is, a little is better than none but too much is dangerous. Some people even think you shouldn't need to feed at all, but the proper foods must contain some stuff that doesn't grow as biofilm.
Hope all this waffling is of some help, i've forgotten what the question was............
Simon