CUC necessary?

As you can tell from my signature I did have a pretty good clean up crew a while back (when I first started the tank). Many have died in the last year and I was curious what type of crew do I really need to maintain once my tank is mature? I still have a queen conch, a few hermits and some snails (cerith and nassarius) but should I be restocking them?

OT: Just added my Coral Beauty today! Always fun to add a cool, new fish!

Thanks!

 

Anything that will clean up uneaten food, remove detritus and microalgae are what you should strive for...Queen Conch are great, except they will outgrow your tank eventually. A Hawaiian or Tiger Tail Cucumber will do a nice job, Sea stars(Brittle and Serpent), assorted small reef safe hermits to get into small spaces in your rock work, the many worms that come with your live rock are an added bonus. Nassirius, Abalone and Margarita snails are good for cleaning up the substarte while Astrea, turbo, Cerith and Trochus snails to remove algae from your rock, equipment and glass along with Green Emerald crabs. Then you can't forget the Fire, Cleaner and Peppermint shrimp either!!! Those are some of the best, I feel to perform an yoeman job at keeping your tank clean.
For filtering your water, may I suggest, Sponges, coral, Gorgonians, feather Dusters and Clams(Tridacna). The clams and sponges especially will aid in consuming Nitrates especially so it is important to have some nitrates in your water!
Believe it or not rgeir are a few species of Moray Eel that will be a welcome addition in a reef tank as well...Snowflake and Chain Link are two of the better, smaller choices which will stir up your space between the rock and on the bottom and remove uneaten food as well,
For your water quality, really the best way to accomplish a adequate level of nutrients is to feed small amounts periodically throughout the day, and any way you can to get detritus etc. suspended in your palegic area of your tank and have it remain suspended there for as long as you can will go far in terms of your tank having low phosphates, ammonia, nitrites and nitrates...Powerheads or other wave/water movement powerheads or pumps will assist this greatly.
As for restocking the snails etc., yes that would be agreat idea to do that, however, you need to be sure of the reason as to why you are loosing all these snails before you go out and get more-to avoid more dead snails-