I bought a 10 gallon tank about 4 months ago. I did this without knowing about the nitrogen cycle and stocked with about 8 fish. After a little research and finding this site I realized I had made a mistake. So now 7 fish have died and the last remaining fish which is a dwarf gouramI seems to be doing ok. Before the other fish died we had what I believe was ick or fin rot or both. This was cured with tetra lifeguard. So now the gouramI is using all his fins and is doing good. About the water...Through out all of this the ammonia has been between 2.0 and 4.0 ppm. Nitrites have been at 0 ppm and Nitrates have been between 20 and 40 ppm. I have used 2 bottles of tetra safestart which is supposed to be enough for 4 10 gallon tanks and nothing. I'v done water changes of different amounts from 2 to 4 gallons of water based on info from pet shop. I'v been using ammo lock between safestart applications. As per instructions didn't use ammo lock for 2 days before adding safestart, then not using again for about 5 days to give the bio a chance to work. I have cut back of feeding to a very small amount 1 time a day and alternate with flakes and brine shrimp. I use a gravel vacuum when changing water. We made the mistake of having to much gravel at first but now only have about 5 pounds. Started with 15 which I think was playing a role in high nitrates. Since cutting back on food and only 1 fish I though the nitrates would go down and allow the nitrites to kick in but has not happened. The water is so clear you can't even tell there's water in it. I have a Aqua tech hang on back filtration with 2 filters. I have changed the foam one once and never changed the fiber one. Just rinsed in tank water when changed water. The filtration is rated for 100 gph. I have 5 fake plants and 1 castle for fish to swim in. I never wash them to preserve the bio on them. I just put a bottle of safestart in the tank about 7 days ago and numbers today were close to 4.0 ppm. 0 nitrites and close to 40 ppm nitrates. Added the ammo lock again today because of high ammonia. Using API master test kit for testing. HELP. How can I get the nitrites to kick in. Thanks for any and all help.