I believe the only thing that can help you are snails. I have a pistol shrimp but he only tends to the burrow and what is about a goby's length from it and he just takes the substrate that falls in the burrow out.
Turbo snails are good for algae (particularly hair algae)
Nassarius snails focus on eat detritus but lean more towards dead and
left over meaty things, they burrow but I wouldnt consider that substrate turnover.
Blue hermit crabs dig around in the substrate and turn it over.
Cerith snails and -- you're on the edge for 25g -- fighting conchs will do this for you. Ceriths do burrow in the substrate in their neverending quest for detritus and algae, and are great overall members of a CUC.
I bought a court jester goby from algae barn a few weeks back, he’s doing great at sifting the sand! Besides his burrow he dug a hole in a corner and is constanly scooping up mouth fulls of sand and spitting them back out. I think they need a healthy supply of pods to go with them as well though…
As others mentioned Conch ( Fighting or Strawberry), your 25 gal is likely not a long term home for them though. If you can strike a deal to get one then sell back to LFS or even rehome to another local reefer, after 3 or 4 months something to consider.... they are workhorses on the substrate, eat voraciously