gobys make a huge mess... i have lost a chalice because of a goby... conch snails are legit, nocturnal and do a good job... nasarius snails are cool if you feed a lot... since they eat everything that lands on the sand, or if a fish dies somewhere you can't reach, they'll eat they all they...
i like to get like 10 hermit crabs and that's it... i never buy more... after a year or so, i'll only have one or two snails max... then i'm cool with them... they won't compete for food or starve because there isn't enough food...
don't ever get an arrow crab... i've seen they eat a fish who was just swimming by... jerks...