Yeah LG is right. A tank of this size will need an enormous cleanup crew
Sounds like alot. People that gets told of the number of snails/crabs they need to clenup feel that the number is far too high."But i wont see any rocks or fish" they say, "All i will see is snails and hemits all over the glass and rockwork". Believe me, this isnt true as they will get lost within the rockwork and cave etc, only to appear sporadically.
Turbo snails, astrea Snails are good workhorses for munching algea on glass and rocks. Get a good number of these. Hermit crabs are good alround scavengers, make sure you have lots of different sized shells for them to swap homes or they will fight among themselves or even "hunt" the snails for them.
Cerith snails are great for keeping the sand clean as they burrow under it etc. They will also come out after lightsout and clean rocks and glass. (there are usually a good amount of cerith snails for sale on ebay.. just choose a repuatable member)
Other cleanup crew worth considering....
Algea blenny (I think in the USA they call this the Lawnmower Blenny?).
A real workhorse and with loads of character. I have one in my large tank and its a real pig! a real fat belly, so bloated that im mazaed it can even swim at times!
Yet it has never yet taken any food i place in the tank. It just gorges itself on the rocks and glass! Fantastic fish. Perhaps add this after a few weeks wen you start to get your first batch of algea growth (which everyone gets)
Sandsifter startfish
Fantastic for keeping sand clean but this is not recomended for a new setup. I usually add mine after 6 months of maturing. They are predators so they need life within the sand to make them thrive. This constant burrowing will keep the sand nice and clean but its not advisable for a deepsand bed as these thigs can seriously do damage to the eco system in a DSB
Urchins
I have one in my tank. Great for eating Coraline algea that grows on the rocks. (I like to keep the coraline under control so the liverock can breath easier)
I have never yet seen the urchin during the daytime but each night he comes out of his cave and when the lights go on in the morning you can see exactly where he has been
Word fo warning though, these things are incredibly strong and you need to make sure your rockwork is very secure (i dont use any bondings with my liverock but its firmly in place)
Again, not something i would add immediately. Alow about 6 months growth first
People recomend Snails and hermits first as they are probably the easiest to care for early on. Get as much as you can to begin with, if you cannot afford such a large amount thats ok, just get what you can. A good rule to follow when considering hermits or snails is this...
Each time you visit your local shop and make a purchase, be it a fish, food or anything, just add 1 snail or hermit to the list, this way its not so expensive and will slowly help to increase the population a little at a time. It also will help to reaplce the inevitable deaths and losses that will ocur that you might not know about as they usually happen behind the liverock out of sight. This way helps to keep the numbers up and running at an efficient level.
Try and get some variety in your cleanup crew also if possible (without causing community conflicts) Each cleanup will usually favour 1 sort of algea etc over another. if you have a large enough population with large enough diversity then your algea troubles will be under control.
(This is the problem i am having with my larger tank at the moment. Not enough diversity as i am still adding to the cleanup crew)