Look at "the claws", amphipods don't have claws, the invert I posted pictures of clearly have more to the "claw" region than amphipods do. I appreciate you help, but I am fairly certain you are wrong....and the antennas look to long for any pod I know of.
I dont think they will be able to grow and go through all the molts they need to become adults ( maybe this is wishful thinking).
I have also noticed some of the larger ones have a red tint to them ( I am also fairly certain I had a mantis or two in my system until recently when I removed the rock they lived in. I also notice a strange spawn one night, I could not ID the spawn, but I know they werent my fire shrimp.
Mantis Shrimp don't curl their bodies up and sit down, like in the first & second picture. Mantis Shrimp also move way different then pods do, something you should notice when one is moving around. You should also notice the difference in the eyes, Mantis Shrimp has big eyes which move around.
How big are they? It's kind of hard to tell from the blurry pictures, but in the last shot you can see some nuances of mantis shrimp features (I think I see claws the claws you're talking about).
The hind quarters of amphipods tuck under their bodies pretty roundly and smoothly (like 3/4 of a circle) while the mantis shrimp has sort of a rounded back with the rest of its hind quarters pointing down. (I was actually going to put up the pictures DLO did.)
IMO, the first two look like amphipods because of the curling, but the third is questionable.
I agree with what you guys are saying, and its possible some are pods...I have seen so many of these things, some bigger than others, and one was even redish.
Marrone: Its hard to tell the movement b/c they go in and out of side, they live in the "sandbed" saw they constantly crawl behind a small rock or something.
Tentacles: They are roughly the size of amphipods
as I mentioned earlier, I had some mantis or pistol type clicking in my tank at night( dozens of times a night) but got rid of that rock, and no longer here any clicking.
From all the pictures you posted it looks like a Pod. Also Mantis Shrimp are consistently on the move. In the pictures that you posted the things is behaving like a Pod would. Also the eyes on a Mantis Shrimp are individual and on stalks, they really stand out and you can tell them difference between a Mantis Shrimp and a Pod.