I don't have the ratio for tuna off-hand, but IIRC a selenium supplement is all you need to counteract a fish-heavy diet. But, yes. You can also supplement fis

I don't have the ratio for tuna off-hand, but IIRC a selenium supplement is all you need to counteract a fish-heavy diet. But, yes. You can also supplement fish with higher sel:merc ratios to balance it out.