Cerith snails would be a great choice since they burrow in the sand also a fighting conch or any other sandsifting invert. How old is your tank? Do you check your ro/di tds?
You might try sand sifting starfish, emerald crabs, Horseshoe crabs, trochus snails or margarita snails. I would get some seachem phosguard too. Of course how many you would need depends on the size tank you have.
I'll see what the store has tomorrow. For now I'll put my hermit crab in the tank to see if he helps. I test the ph , nitrate, and nitrite 2 to 3 times a week. The tanks is between 4 to 5 months. Going to need a bunch for a 46 gal tank. Was looking into getting 6 or so emerald crabs the other day
The refugium will help and run the light at night for it not during the day it helps keep your ph the same. I would look in to an 8 watt UV and a small skimmer.