First I want to say that I think I fixed the problem, but wanted to see if anyone else had this sort of issue. DragonStone problem - > My dragonstone started "shedding". There was a build up of loose chalk like dust that started to grow on the surface of my dragon stone while the dragon stone itself became soft and sort of clay like on the surface. My fish COMPLETELY avoided the half of the tank that had the dragon stone and I assumed it was because it was brighter, or that it had less plants etc. I noticed the dragon stone bits and quickly did a 50% water change after removing them. When I picked the rocks up it created a cloud of snow like material. All of which I vacuumed up and got rid of in the water change. (I do weekly 10-15% water changes so 50% was a lot from my 20 gal tank). Before this too I was having one fish die every few days. They all would just start swimming upside down for no reason then die. I lost 2 long finned danios and one cardinal tetra after adding the dragon stone. After removal of Dragonstone - > My fish are much more vibrant, they are using EVERY part of the tank now without any other changes to the tank. They look much better and healthier and none of them are swimming weird anymore. Water Parameters - > My water parameters were constantly checked especially every time a fish had died this week (I use a liquid chemical testing kit, AND the little glass clings that show the ammonia/ph levels). And my parameters were 0 Ammonia, 0 Nitrites, 0 Nitrates, and 6.9 PH. My water temp is 78 degrees (constant) and the water is treated for heavy metals, chlorine etc. every time I do a water change. All the parameters were perfect before, during and after the dragon stone so my guess is the fish were eating the dragon stone bits and getting sick? Set up - > 20 gallon long tank with over the back filter, water heater, and planted with black gravel substrate. Plants are Narrow leaf java ferns, japanese clovers, and dwarf hairgrass. Lights are on for 6 hours a day and I turn on the lights an hour after turning on room lights, then turn them off an hour before turning off the room lights so the light change isn't sudden. Also note that I bought the dragon stone at a FISH store, not petsmart or petco but a specialized store just for fish only. And they told me that the only thing I needed to do for the dragon stone was to rinse it off really well under warm water then add it to the tank like any other decor. I perhaps should have done a heavy bleach soak or something? But I thought the fish store would be experts on their products. Considering the fish I bought from them might die if they tell me the wrong thing and it would lose them money.