I have had fish delivered from Tropco and also bought direct from there physical location. very impressed. Their warehouse is quite impressive. I have also visited one of the other well known places mentioned on here- and was not in the same league.
So last weekend I tried my solution which seems to work.
Friday evening, Bring 120 litre barrel into through room at opposite end to tank. Fill with RO through slightly open window. Remineralize with tap and bring to temp.
On Saturday I drain water from tank via the extra outlet on FX4. Run...
I make my RO in the garden at present from a garden tap. I 'make' around a 100L. Storing upstairs won't get past Mrs C. It take around 3-4 hours I guess. A large container at height is something I've been thinking about but space again is an issue.
I think I'm going to try pumping with RO straight in. The issue is I have a 2 hour window on Saturdays to get the job done, so if the booster pump does the job it will save a lot of lifting! I use about 30% tap so can use that to adjust temp if it goes to out of kilter.