Your username: Twage In which minigame/server does the bug occur: The new peaceful survival. Detailed description of bug: Likely due to the custom world generation mod having changed the Y-coordinate of sea level, no guardian fish are spawning at any of the naturally generating Ocean Monument structures, except for the 3 Elder Guardians (which are hard-coded to spawn within certain rooms in the monument regardless of location). This makes it (seemingly) impossible to farm guardians for prismarine materials, making the only sources of the blocks a) the Ocean Monuments themselves, and b) the (in my opinion overpriced) prismarine components in the shop at spawn.
I'm not sure, let's leave it to the staff. Next time I recommend looking through some of the previous reported bugs in-case you report the same bug again. Especially for the new survival, since it's a new mini-game, there are lot's of bugs. It's very likely that it's already been reported.
Bug was already reported on Thursday by another user. Due to this, the thread will be locked. However, if you feel like you have something to add to the topic, you are completely allowed to reply to the thread linked above. Cheers, Twage. :)