Hey guys I need help, I have a tank newly established about two months old 20 gallon. I had thought it was fully cycled a month ago when ammonia 0 and nitrite 0 were at zero for several days. I had used old media from another tank of mine to try to speed up the cycling as well. I have 4 guppies, 5 neon tetras, a shrimp, and a bristlenose pleco in the tank along with about 35 week old guppy fry in a fry cage. For the past week or so I’ve been battling a nitrite spike and for the life of me I can’t figure out what’s causing it. I feed the fry and the adult fish twice a day. It is bare bottom so no places for food to get stuck and rot. I have java fern and moss that I thought would help with nitrites but obviously not enough. Nitrites have consistently been between .25-1. I’ve been doing daily 50% water changes. This morning after having done these changes for five days now it was at 1 and I immediately removed the fish and did a 100% water change. This brought it back down to blue (obviously) but then tonight I retested the water and it was back to a light purple so I did another 50% water change on top of the 100 I did this morning. What is going on?! I’m losing my mind! Ive had 4 tetras die on me at this point (idk how they go but I haven’t lost a single guppy fry) please help! What am I doing wrong?