We have nitrites!!

Well the tank is looking dirtier and dirtier.  I suspected things may be happening, and last night I finally have some purple showing up on the nitrites test.  I'll post some pictures of some of the brownish looking sand later.  Still no nitrates, and the ammonia level is still the same.  It will probably take a bit before the ammonia will go down, and then a bit longer still for some nitrates to show up and the nitrite levels to drop.  Here's hoping it will be soon though.  I was planning on pulling the plug and doing a water change and putting the frogs in tomorrow, but I think I'll just stick with the original plan now.