In Glass

[Erthona]

Tetras fletched of cobalt and ruby   (possibly "in" instead of "of", think of how you would say it in terms of an arrow)
shoot through the water.
A tribe of a hundred poisoned blow darts
curve(curving) into a bubbly helix.
An orchid blossoming then molting back, (I don't think "Molting" is a very good word here/mixed metaphor, flowers do not "molt".)
They come and coalesce through the green (water? Just saying the green does not say much. It has not been established like one might use the "blue" when talking about flying in an airplane)
against their fragile plates of glass. (Not sure this says much)
Flowing, swimming,
Swimming and flowing,  (Yeah fish do that)
through the same stones and green  (green is not an object, it is a color, green what?)
they’ve seen since their spawn,  (spawn is used incorrectly here, should be birth)
tracing the same paths millions of times
as infinite as shore break. (These images do not really come together)
As if quietly lullabied in the current,  (awkward sentence, write it out in a single line and look at it)
tendril, waters of Amazonia, (Amazonia is an incorrect word choice. From dictionary.com "the land around the Amazon river". Do you mean "Amazonian"?)
they follow their reflections.

Little souls in the sound of a rippling filter,  (It is great to anthropomorphize, but this one doesn't really seem to work all that well, although I can appreciate the alliteration)
calm me to sleep this night.
I've drifted into sameness (tense change is awkward "I drift into..." Present tense works better as that is what the poem has been in up until this point. Plus it gives the poem a greater sense of immediacy and energy.)
And yet soaked in my own complacency
I've followed, flowed,
Flowed and followed, (Tooooooo much repetition)
Only to awaken and lie awake (Tooooomuch restatement)
in the same unsettled state.
With fingers grazing my damp window,
I wonder in your stubborn grace.  (Who is being talked about now?)

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This seems to start out as a simple imagist description of a specific tropical freshwater fish in an aquarium. One must concede a somewhat huge aquarium for 100 tetras to preform such acts as are attributed to them. I would guess at least a hundred gallon upright tank to have the necessary water column, but maybe the speaker is a zealot or very rich, however this is juxtaposed  to the  aquarium making enough noise to lull him to sleep, such an expensive setup would probably be quite as the top would be capped. Just my thoughts as I was reading, for me a bit disruptive, probably not for others.
I would say the main point was, as I started to say, a simple word painting that somehow towards the end tries to transform itself into Coleridge's "Kublai Khan", or rather his description of coming out of his opium induced  vision. Anyway, has that very English Romantic sort of end to it, with a little Purfrock mixed in for good luck

"...yet soaked in my own complacency
I've followed, flowed,
Flowed and followed, 
Only to awaken and lie awake 
in the same unsettled state.
With fingers grazing my damp window,
I wonder in your stubborn grace."

All in all, this could be cut to about a third of what is currently here and made into a much better poem. Outside of just painting a word imagine, these is little to hang ones hat on. It's a nice image, and no worse for wear, but one should not try to make it into something it is not. There is no metaphorical hook for one to hang ones hat on and discuss things of life et. al..

Allow it to be as it is, work at crafting the words better, being more judicious with the number used.

Best,

dale