Is adding live sand to established tank bad?

[Cannoy]

My 38 gallon tank has been going for about three years now with only 20 lbs of live sand. Today I decided to add another 20 pound bag before my water change. I checked my nitrates a few hours after the change and it went up to between 20 and 40. Is this because I added the sand?

 

[calabdiver]

more than likely yes, you added new bacteria and organisms to the tank by adding the sand so your tank will go into cycle mode again. It tends to happen whenever you do anything drastic. Double your water changes and you should be fine.