I built a 5 gallon, heavily planted, filter less shrimp tank and everything was going fine for 3-4 months. I'm not sure why but my cycle suddenly crashed 2 weeks ago. At first I thought that it would recover relatively quickly since it was only .5 ppm of ammonia and when I cycled the tank I made sure that the tank could process 3 ppm of ammonia in 24 hours without plants. I dosed prime daily and waited a couple of days but the ammonia stayed at .5 ppm so I decided to get a sponge filter. I took some mulm from my twenty gallon and slathered it on the sponge to give it a head start and waited a few more days all the while dosing prime daily. However, the ammonia still was at .5 ppm so I went out and bought some seachem stability to see if that would help. It's been 4 days and the ammonia has stubbornly remained at .5 ppm. Is this normal when recovering from a mini cycle or cycle crash?