The other day I was extremely dumb and decided I needed to change my sand bottom 20 gal aquarium into a rock bottom ( I washed all the rocks thoroughly with plain non chlorinated well water) so I took all the fish out and did a 100% water change in order to spray away all the sand at the bottom of my tank. 2 days later; all 3 of my guppies, my Molly and my angelfish turned up dead. My bristlenose pleco named Spirit is still alive though! I’m 99% sure from looking at some of these threads that I was not supposed to change all of the water so suddenly because it put them all into shock. I’m extremely scared for my bristlenose now because I don’t want him to get sick or die, I loved all of my fish very dearly because I had the privilege of having their moms before them as my companions, so they were all born in my tank. Is there anything I could do for my little guy so he doesn’t enter the same fate as the rest of my fish?