How can you tell if the cycle is over?

[reef dude]

I am sooooo confused about what to do with my tank. its been up for about just about 2 months now, and the only toxin that is really showing up is nitrAte. its about 10 ppm. I know that a lot of things can tolerate that level but will this nitrate level ever naturally go down? i mean its been at 10ppm for at least 2 weeks, maybe more. However, i can see millions of little bubbles floating up from the sand at a rate of like 1-2 bubles a second. I believe this is part of the nitrogen cycle, correct? could these nitrates be high because the nitrogen cycle is not done? this tank has been up for 2 months now, shouldnt the cycle be over by now?
I have 150 crabs and 50 snails in there to take care of my excessive algae growth now, could they be causing any levels to rise?
WHAT CAN I DO TO LOWER MY NITRATES??? thats the big question.
i know i should maybe wait and see if they go down but how long could that take?
should i do a water change, but if i do, would it be bad cuz the tank is still cycling? or is it done cycling, and for some reason my nitrates are high?
can i add some sort of good bacteria sollution from the LFS?

 

[carrie1429]

Does the bottom of your sand or crushed coral have a layer of brown stuff on it? If so your cycle should be finished. To lower your nitrates do a water change and see if that brings it down.

 

[fshhub]

nitrates 10?
is that all, that is like having nothing, do not worry about 10, seriously
if you have no nitrite or ammonia, then 10 nitrates, you are more than adequate

 

[wrassecal]

I jumped for joy when I successfully kept my nitrates at 10! With cc substrate I never got them below 20 and everything was fine. With dsb I have now gotten them down to 10 and even if they never get to 0 I will be happy.