Graybeard, check my thread near the end (its 20pages long right now). Here's the problem:
You have high nitrItes. The test kit you are using (regardless of the make) is not meant to properly diagnose high nitrIte levels. You have two options. 1 you do a serial dilution which is described in my thread. This will let you know approximately how much nitrIte you have present.
2 you do a 90%
PWC and check levels again. If you have been dosing with continuous ammonia (which I suggest), you might have a really high level of nitrIte in the tank (like 20ppm). Even if you cycle is completed, you might still never know due to the HUGE amount of nitrIte present. I would do a very large
PWC and then measure again, if the nitrIte is still off the chart, do another HUGE
PWC. Here's the math behind it:
You did not do almost a 100% water change. You actually did about a 70% water change. This is why during fishless cycling (or when fish are not present in the tank) you get as much tank water out as possible during a change. You cannot add %'s up during successive water changes. So when you did a 50%
PWC, you decreased the number in half (lets say it was 10ppm originally, you decreased it to 5ppm). Now you do a 40% water change (that 5ppm gets decreased to 3ppm).
Had you done a 90%
PWC all at once (and not added water back in between drainings) you would have had 1ppm left. So when doing
PWC's, the % you actually remove at one time is a HUGE factor in how many
PWC's you need to do. With fish its a different story due to stress and territories, but with no fish present its an easy decision,
always take as much water out as possible when doing a PWC as you will remove the LEAST amount of bacteria, and do the LEAST amount of work.
EDIT: Oh and watch out for that "creature" that was in with the plant, if it dies it could skyrocket your ammonia levels and thus nitrIte and nitrAte. Personally I would fish it out and humanely kill it, or put it in another container and change the water every day or so until your main tank is at acceptable levels. Right now, your essentially torturing the creature.
justin