Many aquarists like to amuse their fish with some types of frozen food, usually sold in the form of practical cubes, similar to ice cubes, but smaller.
Let's talk about frozen food useful for marine fish and for freshwater fish .
We use a variety of small animals, the food is definitely more common brine shrimp (both adult and larvae), Chironomus (red worms), Daphnia, Mysis, Krill and others.
It then buy the "blister" of large cubes about 3 × 3 cm and, depending on the number and size of fish that we host in our aquarium will prepare one or more, to be administered as soon as ready, perhaps with added vitamins or other chemical compounds useful the fish (even drugs ... is a great way to treat fish diseases ).
There are blisters mono-species, then with all throughout Artemia or Daphnia, but also mixed, as in the picture, then with 3-4 different foods is still suitable for aquarium fish.
By far the most common food is the brine shrimp ... why? Because it is more likely to be accepted by the fish, but even if it is a poor man as food nutrients. So better NOT restricted to those of Artemia and buy and administer at least 2 different frozen foods, such as a couple of times a week, alternating them.

Then detach the door from a cube-cube ... but we can not throw in the water as it is, for 2 reasons:

1. However, the fish will try to eat him, but it will all agglomeration and thus not all succeed in the enterprise
2. water will melt even the liquid that holds the food, liquid VERY pollutant (phosphates and nitrates) that we can easily do without ...

So ... off the block that should be left to thaw somewhere ... a saucer, a cup (A more specific tassina well ... so the wife / girlfriend / partner / MOTHER you can not complain about).
This then passes the cubes in a colander, then through a sieve of some sort-mesh, to put under the water to clean food from the remaining liquid. At this point we can replace it in advance and maybe addizionarlo cup rinsed with a liquid vitamin. Wait a few minutes and then we can give to the fish, preferably by filtration and circulation pumps off.
Also this phase should not be underestimated because, unlike the commercial granular foods, frozen food tends to fall more quickly on the bottom and is often also of different size and consistency (think for example to a NEON that bites into a little worm Chironomus ...), better to give some 'time trying to get him to everyone.

If you have any questions ... comments are below specifically.