Don't expect an experience like ARH from Sakana. I've read thru both, and I can't let you get away thinking that they're anything alike. Their appeal is totally different.
First off, focus - the threads here on /cm/ may give you the impression that Sakana, like ARH, is principally about a relationship between these 2 dudes. It's not. It's just the main draw for most of the fandom from what I've seen. The actual main relationship is a straight one, though the 2 get similar amounts of screen focus.
Also, Sakana has a larger, more diverse cast, to which it gives comparatively more focus than ARH does to its supporting characters. As it should. Sakana's minors are often just as entertaining as the main cast, if not more so. I mean, Adrian and Carter's besties are very affable people, but it's not for them I read the comic. With Sakana, I'm anticipating the extremely minor Mura's return just about as much as I am an impending coffee date between two of the mains.
Why is that? Well, that brings me to another difference: as a romantic-COMEDY, ARH is ... funny. Solidly, charmingly - chuckles all around. Sakana? Outright gut-busting. It's a cartoon. This, I believe is the main difference: comedy is arguably at the heart of Sakana, not romance. And imo, the most heartwarming relationship in the entire comic? Purely platonic (except in my dreams).