Apologies in advance, this post is kinda long. Here's a summary for those who don't want to read it all:

1. Ammonia level spiked
2. Did 50% water change, removed some fish and decaying plant matter
3. Ammonia level keeps spiking
4. I removed everything that could possibly be generating ammonia from my tank and did another 50% water change, ammonia levels STILL insanely high.

I have a rather bad problem with my 10g freshwater tank. For reasons unknown, my ammonia levels spiked way off the chart and have remained insanely high even after I've done everything I can think of to remedy the problem.

I'm fairly sure I know what started the cycle, I got a pretty good deal on neon tetras, but the fish store employee would only sell them to me at that price if I bought 10 of them. With a 3.5-inch algae eater, a 2-inch molly, and a full-grown tetra already in the tank, I think the introduction of way too many new fish crashed the tank. At the same time, I also bought a small plant to put in the tank, and a big mass at the center of the plant started to rot without me knowing it.

I woke up one morning and my tetras were doing backflips (literally) in the tank, and I freaked out. I checked the ammonia levels, and they were way off the charts.

I removed the tetras to a friend's tank, cleaned up the rotten and dead plants, and did a 50% water change over the course of a week and things calmed down quite a bit, but about a week later (this morning) everything hit the fan again. My ammonia levels remained high, but I assumed it was alright since I had added Ammo-Lock too and the bottle said that even though the levels may read high, the ammonia had been converted to a non-toxic form. Well.. something went wrong, and my other fish started acting funny today too.

Long story short, I've moved the fish to a friend's tank and they seem to be doing a lot better. I did a >50% water change in my tank with conditioned tap water and the ammonia levels are STILL high. This is where I'm starting to pull out my hair. Why would the levels still be high when there's absolutely no dead plant matter, I vacuumed the gravel, and I did such a huge water change?

Part of my problem, I think, was that I used pure distilled water when doing my original waterchanges on recommendation from a PetSmart employee. Yeah, I read up on it, and apparently using only distilled water is baaaaaaaad. But why would my ammonia levels stay so high even when there's nothing that could concievably be causing it?

Could the problem be stemming from my Bio-Wheel? I mean, the Bio-Wheels are supposed to REMOVE ammonia. I've replaced the filter cartridge itself twice since this problem started, the second time being this morning, but my Bio-Wheel has been there all the time since I don't want to have to re-cycle my tank.

All my other levels are perfectly fine. My PH is a little bit on the high side, but that's due to the natural levels of the tap water more than anything.

I just started out with the fish hobby back in September, and I've made pretty much every boneheaded mistake there is to be made. The way I look at it, every mistake I make is something learned, but this is still stressing me out an awful lot.

Anyone know what exactly is causing this, and how I can go about fixing it? I'm tempted to just remove *everything* and start from scratch and add one element of the tank back at a time, testing thoroughly after each part is reintroduced, but that would take a huge amount of time, time that I don't have as a college student.

Thanks in advance for the help!