Hi,
Thanks for your sympathy,I know it sounds funny but I've always been a very careful and loving fishkeeper,I have kept fancy goldfish,marines,Koi and always looked after their wellbeing to the best of my ability,my fish usually die of old age.I introduced co2 because I wanted to improve the growth of my plants and cut back on algae,well I don't know if this was going to happen but since adding co2 I have lost 1 Betta,4 Cardinals and 6 Harlequins.Now I find that quite hard to take on board and I have since decided that I would rather have a tank with some hair algae and plants that sometimes struggle to grow than seeing my fish dying.
Thank you for trying to help but I'm quite looking forward to going back to my uncomplicated,low tech,algae infested happy tank.