The most mogger supplement I know of (poorcels don't enter)

[capycapybara]

Microalgae is what makes fish high in omega 3 in the first place so if you use a microalgae supplement you'll be getting omega 3 straight from the source without needing to ingest mercury from fish. Also has vitamin D3 in it. But it's expensive, only richcels get the benefit of not being poisoned by mercury. https://www.vegetology.com/en-us/supplements/omega-3-liquid-no-added-flavour