In my 200litre planted tank I have bottled Co2 running during the day and turned off at night. Im dropping the spraybar down during the day so nil surface movement and raising it above the surface during the night after noticing fish hanging around surface in the evenings (no gasping at the surface though) Co2 indicator shows correct levels so im not over doing the Co2. I can recall yrs ago I used to leave Co2 on day and night with Tetra species with no obvious problems:icon_redf but Barbs seem to hang more to the surface once the MH lights are turned off? Or is this normal for Barbs?? Just worried there not 100% happy??