My First Set Up

NO2 is Nitrite not nitrate.
And 0.3mg is the equivalent to 3ppm. If that is this case then that is a scarily high value for Nitrites.

and if it was a typo and you actually mean Nitrates...then that is unbelievably low. So basically tells me your tank isn't cycled.

maybe i'm testing it wrong then, when I first put fish in they were gasping at the top and when i went in the shop he told me to take him a water sample when i did and he tested it it was a red colour and he said that was dangerous and i bought one of the kits and a bottle of some kind of bacteria which i was told to add the whole bottle which he said would reduce ammonia and nitrate? I added this and after a couple of days they seemed fine and when i retested a week later then water turned a light yellow colour

have been out today and bought a bigger tank 3 times the size of my old one, Put the water in from my old tank and running my old filter in there alongside the new one plus new water which i've treated the tank is only just over half full with water as I didnt want to add so much new water and just stick them in but all fish are happy now, took the algae eater back to the shop and my rainbow shark has now stopped chasing the rest.

I plan to add 5ltrs of treated water every couple of days is this the best thing to do now?

I'll update with pics later

New Tank

2

Cool! It looks alot better now. Also its fine to add half a tank worth of new water, as the water holds little good bacteria so aslong as the temps are similar you could have just filled it up.

Do you know the measurements of the new tank? How much water it holds? You can also fill it up a little more for an extra bit of water.