SkullJug said:
First off some good news, Your plants won't be affected, They can use ammonia as a source of nitrogen.
The only thing you can do is keep water changing to keep you ammonia at a low rate. Unfortunately keeping the ammonia low enough to save the rest of you fish will also slow you cycle down. Persevere and everything will work out.
Oh yeah, don't overdose prime when you water change, it will bind the ammonia and may slow down the cycle (This is thoery only!)
Am sorry to hear about your angel. Best of luck and stick with it!
A couple of comments. Your plants will most definately enjoy the ammonia (its easier for them to use than nitrAte), but so will the algae that is most likely going to get a foothold in the tank. That's actually not a bad thing since the algae will help to eliminate ammonia from the tank, keeping your fish safer.
I would try to get MORE fast growing plants and put them in the tank. Since your frequently water changing it should not affect your dosing regimen much (I'd just dose more potassium).
As for the ammonia comment, any detectable level of ammonia is more food than the current bacteria load can handle so NO you will not be slowing down the cycle if you water change to below 1ppm ammonia. As long as you don't bottom out for an extended period of time (impossible if you have fish creating waste) you should have no fear of slowing/stopping the cycle.
Dose the Prime as recommended (capful for 50gallons), but there is no fear of overdosing Prime. When you say still too high, how high are we talking? 0.5ppm, or over 2ppm? If your over 1ppm definately dose more Prime than recommended (double dose would be fine). It has no affect on the bacteria's ability to consume the ammonia, HOWEVER, it will still show up as positive on the AP ammonia test since its still present, just not in a toxic form.
The big concern I have for you is your nitrItes will start to climb and this part of the cycle generally takes longer than the ammonia to nitrIte. You need to seriously try to get some seed material from an established tank.
In the meantime, cut feedings to every other day to reduce the waste being produced in the tank.
Goodluck.
EDIT: Are you POSITIVE there are no rotting fish in the tank? They can greatly increase the ammonia in the tank even in a well established tank like yours. I'm sure you have checked this, but its a thought (maybe your biological filter wasn't destroyed during the cleaning, it might just not be able to deal with all the ammonia that a rotting fish will produce).
I just had a recent fish death (or 2 still don't know about the other one), and my ammonia levels were about 0.25-0.5ppm when I got home. I am moderately planted with a well established filter and still was detecting ammonia. I found the fish (well part of it) and removed it, did a water change and the level went undetected by the next day.