In nearby Port Aransas, you can catch baby frogfish in the sargassum, as well as various small silvery things.
Last year in Port A, my brother found a 2' chunk of sargassum and brought it in, and there was a 3" filefish flopping around in there! That was cool. We also found a couple of cute baby files, a teeny seargent major, and a few little silver things I couldn't ID- probably babies from open-ocean fish. To add to that, I found a 3" triggerfish beached on the seaweed. He was kind of dry and I thought he was dead, but then he flipped at me. I put him in a bucket, and he seemed okay after a little while, so I let him go.
If you ever find a patch of water that's maybe a foot deep and still, and there's huge clumps of sargassum floating around, you go and look around in there! All kinds of stuff just swimming between places.
Yesterday I saw a seagull eat the biggest pipefish I've ever seen

I chased that darn gull all over the place, but he swallowed it in the air.
I may take a few of those sargassum shrimpies home with me... Pretty sure they aren't gonna be picky or anything. I have some macroalgae in my tank, quite a bit of it, so they should be okay even if seaweed is needed for their care.