I really need some help as soon as possible. I am leaving tommorrow and needed to be able to leave my fish sitter instructions and I don't know what is going on. First my nitrites were spiking, I did 25% water changes twice a day for 3 days. The nitrites dropped down to 0.5, I haven't done any water changes and it has been like that for 3 days. I haven't had ammonia readings in the tank for almost 2 weeks. I check it this evening and I still have 0 nitrates, my nitrites are < 0.5 and now I have 0.25 ammonia? whats going on? can anyone help please???

There are fish in your tank I assume. You should do water changes to keep ammonia and nitrites at zero. Your tank is still cycling. This is very typical until your beneficial bacteria builds up to a point where it can keep the levels at zero. Then you will only have to do water changes to reduce nitrates.

I'm not as knowledgable as most of the members here so you may want to see what others have to say. I would do a 10% water chang every other day and condition the new water with prime.

I would do a 50% then check your levels. Do you have any other tanks set up? If so use some gravel and some filter media to help speed up cycling.

I had a spike a few days ago and brought it down by multiple 25% water changes over the course of two days. It dropped down to 0.5 and has been there for 3 days. The ammonia has been gone for almost 2 weeks. Then I check today, still no nitrates (even though they were there a week ago) and I have 0.25 ammonia. The strange thing is this. I tested pure tap water afterwards and found that I have .50 nitrites in my tap water! What do I do about that? Since I brought down the spike to 0.5 (which is apparently already in my tap) and then suddently small amounts of ammonia show up did I restart my cycle? I did a 20% change this evening. What in the world do I do now without killing my poor fish?

Larger water changes won't hurt. Do as much as it takes to keep the Ammonia 0. Also what type of test are you using, liquid or strips? If you are only going to be gone a couple days I would hold off on feeding until you get back. I does sound like your cycle is between the first and second process and with the nitrite readings I suspect that this is what is causing ammonia spikes. Use Prime as it helps make the ammonia non toxic and reduces the effect of nitrites and nitrates.

Are you disturbing/cleaning the filter and beneficial bacteria? Leave the filter alone as the muck and gunk is actually good unless it clogs the water flow - then use tank water to rinse it off (use the "waste" water from a water change). Remember chlorine will kill the bacteria - don't dump the fresh water into the filter (my brother did that...). You could try buying some "cycle" which has bottled bacteria and gives a "boost" to the cycle. I prefer to use the filter cartridge/media (or even the brown sludge from an established filter will work) from an established tank.
If possible, you can shift some fish to another established tank to reduce the amount of ammonia they are producing - at least while you are gone.
Are you using drop testers or strip testers? (If strip, I advise throwing them out and getting drop).

I had a tank that wouldn't cycle for 6 months, I finally figured out that the water in my HOB filter just went around the media, I changed to a Rena canister and it cycled within 3 weeks.

Best of Luck!

It's all in the quality of the strips, I think. My grandfather scored me a pile of super fancy strips from when he used to work at Rohm and Haas (as a chemist) and they blew the drip kits out of the water.

If the tank is still cycling the ammonia level should rise. Once the bacteria spreads the ammonia level will go down and the nitrite level will rise, as the second group of bacteria grow these level will also drop. The cycling is complete when both the ammonia and nitrite level are at zero when water is tested and the nitrate level are at safe readings. At this point it is important to do proper water changes to maintain your tank.
To many water changes in the beginning can effect how fast the cycle will take. By reducing the amount of ammonia in the take you are removing food that the first type of bacteria need for the colony to grow, this is the same for the bacteria that feed on the nitrite. I would suggest seeding the tank with some filter media or gravel from an already established tank. If you are just leaving for a week or 2, just have the sitter feed every other day and do a 25 to 30% water change ones a week.
If this was an established tank it could be a number of things over stocking, over feeding, improper filter care or untreated water has killed of a large part of the bacteria colony.
What size is the tank?
How many fish are in the tank?
How long has it be running?
What type of filter are you using?

Good news all! That last tiny ammonia spike seems to be at the tail end of the cycle. My tank cycled and the nitrites finally read 0 on Saturday. So now I have 0's all across the board. I still don't get how my nitrates read 0, but I was told the API freshwater kit isn't really reliable for nitrates under 10 so I am gonna have to assume that is the problem. Thanks for all your advice. I am absolutely thrilled it is finally cycled.

Great news. If the tank was heavly planted you would have 0 nitates.

Great news! Keep a close eye on your readings and keep testing to make sure you don't get any more spikes.