Reptile & Amphibian Forums

So I've had a new 16-gal tank set up for a week. I added Cycle and Seachem's Neutral Regulator when I set it up. Two days after setting up the tank, my test kits indicated that all ammonia was gone (I have it in my tap water), so I added 3 albino corys and 2 dwarf gouramis. Since then, I've not had a single trace of ammonia, nitrite, or nitrate. I've been feeding the fish twice a day, and the corys leave bits of their shrimp pellets down into the substrate. According to everything I've read, there should be at least SOME ammonia building up, getting the nitrogen cycle going. I'm confused as to why I'm not detecting any, ESPECIALLY with 5 fish in there, as well as a bit of uneaten food. Any ideas?

It takes a lot more than 2 days for a new tank to form enough bacteria and enzymes. It is normal that for the first few days no ammonia would be detected, even with fish and food in the tank. The reason is that, for ammonia to form, first you need the enzymes and bateria that decompose the uneaten food, which would produce ammonia. Fish do secrete small amounts of ammonia in the urine, but in a it takes a while to build up to a point that is detectable.
Once ammonia starts being produced, especially from food and fish secretion decomposition, you will notice that it will tend to build very fast.
By the way, putting Cycle at the begining may not be very helpful. Cycle works by dumping nitrifying bacteria into the water. However, without ammonia, the bacteria simply dies. Bacteria (nitrifying) should be added once ammonia is detected.
Depending on the tank size, it may take 2, or more weeks for the tank to fully cycle. The smaller the tank, the longer it may take.

Where did the ammonia from the tap water go? I have a kit that detects both ammonia and ammonium, and I know some conditioners turn ammonia into ammonium... but the original 0.25 ppm that i detected at first is gone now.

That's a good question. I did an experiment several months ago in a small 2.5 gallon aquarium. I put water on it, a filer with carbon, and a small ammonia (pure kitchen ammonia). I didn't put any gravel, or sand. The ammonia reading start at just below .50 ppm. Without adding any chemicals, overtime, the ammonia reading went to 0.0 ppm. Since ammonia can evaporate, my theory is that, that's what happened. Of course, once you have fish, ammonia would be produced faster than it can evaporate, or be absorbed by substances (gravel, filter, plants, etc) in the aquarium.
So, the reason your tank didn't show any ammonia, it may not be that the tank cycled in just two days. The nitrifying bacteria, itself, takes 24 hours in good conditions (plenty of ammonia and 80F water temp) to duplicate itself.