im unsure why the issue exists, if it is because of py, water fill mod or alien biomes but with this mod enabled i cant landfill water at all. it uses up my resource but it stays shallow water.

Would you mind sending me your savegame so I can check what's happening? Upload it somewhere (Google Drive, Dropbox, something else) and share a link to it here.

https://easyupload.io/wma9qg

i have a few mods, so be warned. but one of the 3 i mentioned is likely the reason (or something when using them combined, no idea)

Thanks, I'll check it out later today.

Most likely what's happening is that the tile you're trying to landfill is not one of the water types from the base game, but a water-like tile added by one of the mods, which isn't supported yet. And because of Space Age related changes to the mod it also doesn't pick up that tile anymore as something that it needs to replace.

I'll probably just have to add support for those mods and then everything should work again.

Yeah I see now. The base game contains two water tiles "water-mud" and "water-shallow", but by default these are not used in terrain generation and cannot be landfilled. One of the mods, I haven't looked at which one yet, adds these tiles to the allow list for landfill, probably because it uses it in terrain generation.
When Space Age is installed these two tiles can also be landfilled.

I'll make an update that always adds these two tiles regardless of whether Space Age is installed, as the tiles are in the base game tileset.

awesome! thanks for checking it out :)

It's gonna take a bit longer to fix as I found another bug thanks to your save file, sooo thanks for that ;)

Alright, both bugs should be fixed now and landfill should be able to replace shallow water and mud again. Unfortunately I can't do anything about the existing landfill in your savefile.