No Eyes to The Abyssal Zone

[Brownlie]

Ok, here we go then. 

No Eyes to The Abyssal Zone.

Monday knights fight Tuesdays never-ending; they -- I'm trying to figure out what the implications are of metaphorical Monday knights fighting Tuesday's never-endings or never ending Tuesdays. Not sure on the line break at they, I guess it's ok.
run strafing runs down submerged residential blocks -- You might be able to get away with the repetition of run because it apparently has the longest entry in the OED. 
in the middle of the night. And the sun never rises;
they’re in a fish-tank looking at the surface.

And the rafters on the surface look like eclipses, and -- Not sure about the sentence/ transition here starting with "And". Interesting imagery here, though. I suppose looking up from inside a fish-tank could look like an eclipse.
the man-o-war and manatee birds, without wing- -- Not sure what a manatee bird, could be something though.
beats, just contrast leviathans casually sliding
their way off into the humming blue crush. -- I  assume you meant blue crush as metonymic way of referring to the ocean. I guess you want to be getting the most out of this last phrase because it's the end of a stanza. So I guess you could consider if blue crush does that.

And an unremarkable Sunday snowset rises from -- Ok, I thought a sunset looked like it was going down into the ocean. How could a snowset, in the ocean or another sea, rise? Maybe you meant to have the question in there, not sure.
the sea floor, all while naïve skin flakes
float down to feed all the bottom-scummer
weakdays that slither on the plastic pebbles;

there,   if they dug beneath the rocks,  they’d find the sand had turned to glass. -- Not sure about this ending it seems like it was done quickly. I wouldn't really change the fairly regularized stanzas so quickly unless it's a thought out decision that you think really benefits the poem. 

I'll give you a brazen suggestion for the sake of critique. Why not call the poem Fish-tank, and make the thing about a fish-tank or the word fish-tank. I'm not sure how the days of the week are working here, but a large part of the poem seems to about inside water. Maybe providing a concise topic will improve things here.