Let start this off by saying "Mysis or brine are not bad for your fish and inverts, they just dont supply what they need".
I see people all the time posting comments or asking questions about feeding mysis shrimp or brine shrimp in your reefs. Most of the time it's similar to "I feed mysis twice a day and they love it". Well, your doing it wrong!
Mysis and or brine shrimp both are good if you got a picky eater or something thats not wanting to eat what you have to offer. But, its because it looks, smell's and taste similar to tiny critters that they would find in their natural habitat. Not because its good for them. In face both Mysis Shrimp and Brine Shrimp offer very very little nutrional value at all for your inhabitants in a marine or reef tank. Mysis and brine shrimp both only average 4% protein and some manufactueres cloud your judgement by saying things like 36% protein dry based measurement. Well even that isnt great, because its based on the package size, and the fact they are no longer dry once you get them, they are fozen in water. Pure and Simple, really not a good source of food for any marine or reef system. Good to get finicky eaters to start feeding, but not good for long term feeding in your aquariums.
You need to focus more on providing a varied and extremely mixed up diet for your aquarium inhabitants. Not just one food or one type of food. A VARIATION IN THIS CONTEXT MEANS MANY DIFFERENT BRANDS, TYPES, STYLES, SIZES, TEXTURES, NUTRIONAL VALUE, COLORS, VITAMIN ENHANCED......ETC ETC.
One of the easiest ways to do this (but not the best) is to use a premixed frozen food that already has a broad mixture of food sources in it. Two examples of these types that I use are LRS and Rods foods. They are a premix variety of foods that contain everything from forms of mysis and mysid, actual fish meat, roe, rotifers, squid, krill, clam, oyster, vitamins, minerals etc etc. Which you cant deny, a variety is the best thing.
Now, my personal opinion and only way I feed all of my fish tanks wether its fish only or full blown reef is by combining some of all of them. I use both Rods Foods and LRS, but also put in some small pellets, but sheets of nori and dice them up, brine gutloaded with spiralina and as always a few drops of VitaChem.
NOW YOUR GIVING YOUR CRITTERS A GOOD VIABLE FULL VARIED DIET!
With that said, DO NOT thaw your frozen foods to mix them and then refreeze. This breaks down the natural products and actually prematurely starts a premature breakdown of the products. Instead take the time to cut a little of each one daily or alternate which one you use each day.
Next tip is dont use the water aka juice from your frozen foods when feeding your fish. Use a thawing cup or sieve like these to thaw your foods and drain the juices down into the cup. Some say the juice aka water is good for your reef, so with that said, do this instead. Thaw your frozen foods in a Thawing Cup, then save the juice and use it to spot feed your corals with. Now your getting a good actual use from it, instead of it just diluting down into your aquarium water driving those nutrient levels your already fighting up even higher.
You can get these Food Thawing Sieve's at JustFish or on our website at... http://www.aquariumtanktools.com/product-page/tanktools-frozen-food-sieve