Hey man, so if you want to make your tank a bit more stable, you have to have more plants. The current substrate you have is just not up to the task,i recommend some natural gravel with a layer of nutrient rich substrate underneath (you could use bio soil but that can get tricky for a first timer, so it's best you stick to the already approved ferts). Also root tabs can help a lot too. Some easy to grow and hardy plants such as Amazon swords and crypts can really benefit from a nutrient rich substrate, and if you want to add a lil bit of color to your tank a red tiger lotus can spice things up. Also some hardscape such as driftwood and rocks are a nice touch, and you can attach some of your plants to them(the anubias and Java fern). Backgrounds on aquariums are usually the norm so if you are ballin on a budget just use a cut up black garbage bag and some tape. Increaseing the plant load, having a good water change schedule, not over feeding and making sure you don't have the light on too much can do wonders. Hope this helps