So this is my first post here, hello by the way.Sorry if this is a book but I am out of ideas on my tank and it is discouraging, expensive, and I don't feel like fish are safe in my tank and I cannot figure out why and that bugs me worst of all, I dont want my fish to suffer . I will try and give every bit of info here that I can and maybe you fine folks can help. Tank and equipment: 20 gallon long with aquaclear 50 filter and a heater. Water is usually always around 75 degrees. Substrate: 2 bags of Carib-sea Eco-complete w/ lavarock in a mesh filter bag to prop up one side (more on this in a bit) Decorations: Mopani driftood (that ive boiled the out of) 2 flat rocks that I have propped up to create a cave Plants: 4 amazon swords along the back of the tank. Anubias that I have split up and have around the tank 3 of them glued to holes in the driftood (made sure to use safe super glue(fish were dying before I did this anyway)) Water Parameters: I'm a little confused about this part and I don't remember off the top of my head EXACTLY what they were but I've used test strips as well as bought an API master test kit and I do remember they were all in safe levels. Looking at a picture of the results I do have rather hard water with a ph of 7.0 I believe, nitrates looked to be 10ppm, nitrites were 0. I do have a rather bad green hairlike algae issue coming from my plants and brownish algae on the lower back of the aquarium. I don't know if I didn't let my tank cycle enough when I first got it. Basically this is what happened. I took my old betta tank and took the plants and driftwood from that. I watched a youtube channel that seemed rather popular recommend using lava rock below the substrate to prop up one side, I thought it was a great idea so I did. I bought a bag of lava rock from home depot (I think this is part of my mistake) and set up my tank. I let it sit for about a month...probably way too short and I bought 12 red crystal shrimp because I've always loved those. 1 died a day until they were all gone. I went and bought black neon tetras because I heard they were hardy and if my tank wasn't cycled they would help with that and I wouldnt risk their lives. Sure enough they did fine, everything seemed wonderful! I went and bought a dwarf gourami...dead within 3 days, it never ate aside from day one. Water tests were normal. I thought maybe it was petco fish being petco fish. I bought a dwarf crayfish from my LFS...dead within a day, then my neons started dying. It couldn't be my plants, I trusted the substrate, my water is hard but I don't know enough to know if that matters and im stressing I didn't let it cycle long enough. Then I thought about the lava rock I bought from Home Depot, a friend who is familiar with fish recommended I remove it to be sure. I took it out and this huge plume of red went up and colored the water. I boiled and washed this stuff like crazy so I don't know what that was. My remaining neons all bloated up within an hour. I was horrified to see that I caused that to those fish. I went online to look up what to do and people who had similar issues, from what I could tell was dropsy, though THAT was awfully quick, were told to euthanize the fish but most were dead before I figured out what to do. I stirred up the water, and did numerous big water changes and siphoned water from as deep below substrate as I could. I thought things were fine so I bought some peppered cory catfish from petco and some silvertip tetras from my LFS, they lived for about a month happy and active, eating every day before I found one cory upside down. I went to remove it and it swam off, perfectly fine. I even laughed about it, joking how they were messing with me. Next morning, again upside down. This time it couldn't swim away upright, it was dead by the end of the day. Two days later another cory died the same way. All of my silvertips are fine, though one is noticeably more pale than the rest. I went home last night and a cory was dead on my filter intake. I just can't take this anymore. I was going to buy a 5 gallon tank and filter, transfer water over and move the surviving fish there and start my 20 gallon over with just aquarium gravel and fake plants. I am concerned whatever chemicals may have been in that lava rock has just seeped into my subtrate and possibly into my filter media as well. Anyone have any other ideas on what could be doing this? I'm not very enthused about this hobby right now .