Last few days been monitoring my aquarium perimeters, Friday was at 0.25ppm and today its around 0.50ppm, the tanks 7ftx2ftx2ft, i have a huge bio load of 4 oscars 2 plecos and a few smaller fish, but my water change schedule is 80% water changes every second day, i've never read ammonia in my tank before, and if I have my water change wipes it, i have tested my tap water (0ppm), my other water perimeters are fine, 20-30ppm nitrates, 0ppm nitrites ph fine, i use prime with my water changes, i gravel vac twice a week, the tanks been running for 3 years or so, all the oscar's are around the 30cm mark, the pleco's are at 25cm, so yea i got no idea what's going on, any help would be awesome, and if you need anything else out of me i'll be monitoring this thread heavily, cheers guys!