Hello all. I’ve had this 20L for at least 8 months. I’ve had numerous deaths. I started with a fish in cycle. I know that I have constantly broken the cycle which caused most of the deaths with my neurotic cleaning regiments. I would pull the HOBs & clean the heck out of them, getting rid of the slime every couple of weeks. I never used an API master kit. I was just winging it. I was cleaning the foam & sponge with tank water. Now the fish were never dying in bunches. It would be just one here one there weeks apart. The plecos would kill & eat the snails until the plecos died even though I fed them algae flakes. I must admit not all the fish would die just the least hardy ones. The angel fish & the gold fish never winked an eye at me, the worst fish keeper. I was using a water conditioner but it wasn’t Prime. I recently received an API master kit from my mother in law when my brother in law moved out she asked if I wanted it & I said sure. I tested my water & I almost died. PH was at 6 or less, ammonia at 2 ppm & no nitrates. I kicked myself in the ass. I tested the tap water & the ph is 7.5 but after it hits the tank in 24 hours it drops to 6 or less. I have 2 hobs & 1 aquarium co-op medium sponge filter. I said ok let’s fix my mistakes. I left the sponge filter alone since I just cleaned it the week prior. I replaced the foam sponges in both the aquaclear 50 & 20. I was using 2 foams each in both, filter floss but no bio media rings plus the foam was literally falling apart & super soft. I cut a piece of coarse foam I purchased from aquarium co-op, the big black coarse foam square that is around 1” thick. I placed 1 new aquaclear foam on top of that, a sheet of floss & I bought the aquaclear bio-media, placed on top of that floss. Told myself not to touch it for at least a month but I did swap the floss once a week. I do have about 8 live plants in the tank. Some Amazon sword, Java fern & some others that I forgot what they are. I also noticed that they were getting brown & yellow leaves recently so I had to trim them to get the bad ones out. I kept reading about my ph problem. I didn’t have kh/gh test but by reading these forums I figured my city water is junk on gh/kh after 24 hours. I purchased a large Wonder Shell & some crushed coral. I have pool filter sand as my substrate so I sprinkled the crush coral all over the bottom, at least 3-4 cups worth. It was rinsed before I put it in the tank. I have been doing 25-45% daily water changes for a week then I cut back to changing water every other day. I have been testing the water everyday & I have been seeing some great improvements. Now I must say my city uses chloramine & there is ammonia present, .50-1ppm out of the **** tap. Thank god we always drink ro water bottles & there is a filter on the fridge for ice. After about two weeks of testing & leaving the hobs & sponge alone here are my results today. I did a 35-45% water change yesterday. None today. I started using Prime once I found ammonia coming out of the tap.