I had tried almost all the best & expensive types of shrimps food but I find that they still prefer the cheaper Hikari even though they are not that good or nutritious.
I have two which I think are the best
Dennerle Shrimp King complete and Glasgarten Shrimp Dinner pads. But the shrimps don't seem to be interested....LOL
Here is a list shrimp foods that were tested by someone. You can see the test results here.
www.practicalfishkeeping.co.uk
Below here is a link of most of the shrimp food. This is for your quick reference on the food information, ingredients and prices(in SGD) as this shop is not in the UK.
There are about 60 types of shrimp food listed here.
Staple and supplementary food for upkeeping of ornamental shrimps such as cardina, neocaridina.
green-chapter-shop.myshopify.com
I think most important in selecting shrimp foods is ensure that you have all the different nutrients from different food and brands.
For more details information about the nutrients require by shrimps, you may want to search the manufacturer websites.
I also like smaller or fine shrimp food (size: 0.1-0.8mm) that can be given to all the shrimplets or smaller shrimps that can't compete with the bigger shrimps.
For this, I bought the cheaper Dennerle Crustagran Baby.
I also have some shrimp supplements/ foods that are specially high in Calcium for proper molting.
If I remember correctly, Kale, Mulberry leaves are also high in Calcium.
Once in a while, I will also feed them with fish food that is higher in Protein. This is probably for females that are carrying babies.(if I remember correctly).
Lastly, don't forget to get Beta-glucans for immunity of the shrimps.
Glasgarten shrimp fit has Beta-glucans but I bought another Taiwanese brand that is available at a LFS nearer to my house.