The issue of fasting is of interest not only to converts, but also to those who have believed for many years and, it would seem, have studied the church rules and regulations well. The fact is that many products, which until relatively recently it was possible to read about in a historical novel, have become available, and it is not always clear whether they are lean or fast. For example, many believers are interested in the question of whether shrimp eat in fasting.
Old Testament Rules
In principle, the precepts of the Old Testament concerned the Jews. However, it is also part of Christianity, and its establishment, it would seem, should be respected by the church Christians. So, the Old Testament in this respect is very categorical. Can shrimp be in the post? In no case, and on ordinary days, they are prohibited. The main permitting sign for aquatic animals was the presence of scales. But shrimp do not have it. Therefore, they were considered unclean animals and were not eaten.
However, the apostle Peter received a vision in which he was told that the eating habits of people should not be an obstacle to baptism. Therefore, at the council of the apostles in Jerusalem, it was decided that non-Jews should not abandon their culinary traditions. And in everyday life, the use of the same baptized Greeks or Romans of marine inhabitants is not considered a sin. But is it possible to shrimp in the post - it's a completely different matter.
View on the question from the point of view of the Greek Church
When Orthodoxy took shape, “marine bastards” in food were absent as a class. Therefore, clear guidance in this regard does not exist.
Since Greek cuisine makes extensive use of shellfish, crab, and shrimp (in the Greek church there is even a special name for them - “turtle-skinned”), in solving the problem of whether shrimp can be fasted, it is better to focus on their rules. These products are allowed in Greek tradition on the same days that vegetable oil is allowed. This is recorded in the Nomocanon, and such a rule is quite suitable to resolve your doubts.
Strict ban
As for other products, it exists in the first and Holy Weeks, in which it is supposed to eat only vegetable, vegetarian food. In addition, if you fast according to all the rules, do not forget that on Monday, Wednesday and Friday only cereals, vegetables and fruits should be on the table. Since seafood is clearly not of plant origin, these days they are not served.
Different answers to the question
It should be noted that in different parishes they do not look at the tasting of “cutaneous” differently. Some pastors believe that shrimp in fasting can be eaten on the so-called fish days. Others firmly and uncompromisingly forbid them at all, since traditionally oysters, crab and shrimp were considered a luxury aimed not at satisfying hunger, but at satisfying gluttony. If you look at seafood from such an angle, they really have no place on the lean table.
However, many Athos monasteries allow monks to eat marine reptiles during Lent. Some Russian monasteries operate similarly. So, probably, it is not a sin for laymen to taste "skull-skinned". However, if you still doubt whether shrimp can be fasted, consult with the priest of your parish. Since you cannot resolve this issue for yourself, follow his advice.
In conclusion, we can say that shrimp in fasting is the same as wine in fasting or meat at the same time. Orthodoxy does not put pressure on parishioners, but only recommends. Hard work, recovery from illness, low age of children or women “in position” - all these nuances give relief for fasting. And if you eat the same marine inhabitants not because you really want to, but just to maintain strength, you are already observing fasting.