I've never heard that about the oxygen in the water before - I'm learning something new every day! I'll be sure to take this advice on board for my water changes in the future. For example, I use 5L bottles to store my new water in for about 24 hours before a change but I always close the lid, I should really be leaving it off right?
Sorry if this classes as a threadjack!
No not at all
Fishy is looking a little better now hes swimming with his pals again . maybe not as straight as id like but hes improved greatly and they aren't gasping anymore so all good so far thanks everyone .
/www.atlantech.ca/public/articles/Dissolved%20Gases%20in%20Aquaculture.PDF

. the light in there is just an energy saving bulb it isn't a tube like my other tank. the only other thing i can think is the PH being low but im not confident enough in fishkeeping to mess a round with that really.