Ah!! That makes more sense and gives everything a chance to settle down a bit before doing the next water change, so go with that!
The zerowater jug produces the same as RO so you don't need to buy an RO filter as well, so I would start with the zerowater and see how you get on with that. You may later decide to go the full RO filter if you are using a lot of RO water, ie if you decide to also do the large 190L tank but that is too far off to worry about yet!
Just stick with dechlorinated tap water twice a week until the tank is cycled/ready for now and put the zerowater jug and GH//KH+ (when they arrive) to one side ready!
I did order a zero water jug but it hadn’t arrived yet. The only reason I’m doing the water changes is following a YouTube video of a bloke doing the same set up and when he first started he was doing daily water changes. Do you think I should do less? I’m slightly concerned about the ammonia levels spiking.
I thought you bought a zerowater jug filter, that produces the same as RO water, or maybe I have misunderstood? I wouldn't use the filter if it is zerowater jug at this stage as if you are changing 50% of the water daily that is a big waste! Until the tank is cycled/ready you may as well just use dechlorinated tap water but I'm not sure why you are doing daily water changes either?
Quick update on the tank. Tested water this morning and it’s reading 0 nitrite 0.5 ammonia and 5.0 nitrate. I’m doing 50% daily water changes with filtered tap water until the cycle completes then I’m going to use RO from then on. My local shop sells RO water for £4 for 25L but I’m going to buy a unit for about 60 quid.