astol, I see you are only following 4 tags, and no hubs. Posts are primarily filtered in Hubski by following people. Tags on the other hand, are open-ended.

I take it you want to ignore some tags, but not necessarily the people that posted them. That's a tough one. The number of tags a user ignored could get very large. Although you block #marinebiology, #sealife might get through then need to be blocked also, then #whales, #dolphins, #thesea, etc. It would become very convoluted if every user had a very complex subscription formula. Also it wouldn't be very apparent what the users you followed were really posting or sharing, and that would begin to diminish the point of following users in general.

I'm looking at your feed, and I don't see Saydrah's #marinebiology post. Currently, you aren't following her, #marinebiology, or anyone that shared it. The only way you should see it, is if it passes through as an external post (the light blue ones). If you follow someone, you get the whole package, so you should choose people with some care. What I suggest, is finding someone that posts and shares stuff that you like more often than not, follow that user, and begin to follow other people from there. Importantly, if someone is sharing and posting stuff you don't like, unfollow them.

Hope that helps.