Wot he said! I think extra sterilising is a waste of time and you risk tainting the plastics in the system with nasty flavours. This happened to us with an older caravan and the water which had been perfectly drinkable before sterilisation was rendered permenantly undrinkable.if you normally fill with chlorinated tap water there is no need to bother . you could fill it and leave overnight then drain it and refill if you think you may have inadvertantly added un pure water.
I certainly wouldn't ignore it at all. There are lots of simple products out there that you can add to a water tank to ensure you kill off any black spot, algae and bacteriaThanks all. I just assumed the tank would be grotty and the water stagnant.
I'll leave it alone.
Another job ticked off the list.