Well the container is going to be on the balcony, so will get sun.. plans are to mix 100L at a time (100L container, go figure ), and use it from there, topping up/re mixing when needed.
The powerhead I have for mixing it will easily pump water from the container to the tank (I've used it for such before ), so that's all good in terms of not having to move the container.
Temperature wise, I found that changing 10% in that tank when it was freshwater straight out of the hose dropped the tank temp maybe 0.5 of a degree.. is this a big issue for saltwater - I'm happy to run a heater in the container before changing if it is.
Thoughts?