Hello all! First time poster month long lurker here. Sorry in advanced this is going to be a long post. I am having some continuing trouble with my 29g long tank. I've had it for a few months and have had multiple fish die for seemingly "no reason". Okay a little back story. I started this tank about 2 months ago and used "safe start" to get my cycle going. I was advised by the LFS that this was a good product to use and will help get some BB going to help my cycling go along. He sold me about 12 fish (4 tiger barbs, 4 cherry barbs, and 4 of something else I can't remember currently) and said expect to loose some which I was skeptical about. Well we lost about 4 and all seemed well with the tank. I was advised to wait 2 weeks and to bring a water sample in when I'm ready to get some more fish. We did and the water checked out fine according to the shopkeeper. He then sold us 2 Bala sharks, 2 rainbow sharks, and an iredescent shark. Soon after problems arose. The first round of fish we got slowly began to die. Until I was left with nothing but 2 cherry barbs and 1 rainbow shark and the iredescent shark. Then came ich we began using the ich treatment and it only took the I. Shark but then the cherry barbs suddenly died (from a cause other than ich I believe) I was left with only the rainbow shark. I had my water tested by the LFS and they said there was some nitrite and my tank had gone through a mini cycle. So I upped my frequency with the water changes doing about 33% a week. Rather than 50% bi weekly. All seemed well so we got 4 more tiger barbs the next week and the water tested perfectly. Within three days I was down to 1 tiger barbs and the rainbow shark. I finally pulled together the cash to buy an API test kit and have been doing the tests myself for the last two days note that I have been doing 25% water changes every other day since my tiger barbs died. Last night I tested and had .5-1.0 ppm ammonia, .25-.5 ppm nitrite and between 20 - 40 nitrate. Sorry for the inaccuracy I did it late in not the best lighting. After seeing my water test this bad I figured I needed to do something quick and immediately did a 50% water change. Following this I tested and got A(.5) NO2 (.25) and NO3 (20). At this point I'm stuck I need help. I though maybe some plant life would help or perhaps I need more filtration but I'm really at a loss at this point. TL;DR read the last three paragraphs my water levels are bad and my tank had previously cycled completely.