Betta Baby

I rescued a baby betta from Petco about 4 weeks ago and he just died yesterday:(  I named him Rocky, my little fighter.  He was pretty weak when I got him; I also bought another baby plus 3 adult bettas my son, Eric , picked out that were the healthiest...all the rest were dying or dead in those little cups they keep them in.  The other baby died not 5 minutes after arriving home and I spent most of my time with Rocky trying to make sure he was eating and his water stayed warm.  The guy at the store said he would eat the pellets the older fish ate and I soon found out that was not true, so I researched to find out what betta babies eat and found out they eat microworms but it would take a few days for me to get them because I had to order them.  I finally crushed betta micro pellets and fish flakes and read that they also eat egg yolk and that is what I fed him.  He seemed to do well and then he would act weak and not eat and then come around. Once I thought he died because he was belly up and when I grabbed the container he was in he flipped back over but kept flipping on his side.  I stayed with him a long time keeping him right side up and finally I stuck his net in the container and put him in propped up by his little plant.  When I went to check on him, I knew he must have died but he was out of the net!  He seemed to be okay for a few days and then got sick again and this time he died.  I feel so sad about it and angry at the pet stores for selling these fragile little babies they know nothing about caring for.  This has to stop!  I'm forced to carry the burden of needing to rescue these bettas and feel responsible when they don't make it.  I can't even bring myself to go into pet stores just because I can't stand the sight of these poor fish suffering, no, I don't have to look but I know they are there.  Everyone needs to band together to stop these pet stores from selling bettas if they can't provide better ways of housing them and educating staff on how to properly take care of them.  Below is a picture after Rocky's last recovery and 5 days later he died.  My sweet Rocky.