When to add a cleaner crew?

[RedDmon]

Maybe it's a stupid question, but here goes.
I'll be starting my 75g cycle next Wednesday. How far into the cycle is the best or recommended time to add a cleaner crew. Are there certain parameters that have to be met before doing so? Does the cycle have to end before they're added?

The real reason I'm asking is a buddy is taking down a tank and offered me some snails and crabs etc.

Red

[Sophie-G]

Are you using live rock?

And how old is the rock?

The snails/crabs will need to eat...so a new tank MIGHT not have enough food for them...

But...

If you didn't pay for them...

If it was me I would throw them in after a few days...

But...I have never seen a cycle in the two tanks we have set up....

Either that or the cycle was really quite and I missed it...

But the live rock we always used was good quality and was always old and matured...

[Aquarist007]

you monitor your ammonia and nitrate levels. The ammonia level should rise with the curing of the live rock, then fall as the nitrate level increases. when the nitrates fall to zero you are good to add your cuc.
usually after the third or fourth week of cycling

[Michael]

the norm is 4 weeks, obviously though the tank has to have cycled, you will probably get brown algae on rock, when you do, cuc will help out, i have read so many threads on start ups i have been brainwashed now, seriously though wait at least 4 weeks