Exactly, I can always change my RODI approach but presently the ease of having it made and delivered works with my current family situation. I have a 3yr old son and my wife is currently 12 weeks pregnant with baby 2
Why will I need to mix salt, when I'll have all the water at hand ready made. Please tell me if i'm missing something obvious. This is all learning for me and its a steep learning curve, especially when I get the tank running.
Wow - Cheers and Congratulations with the new one on the way. So exciting. Your life is going to be soooo busy. New tank and two little ones. It doesn't get any better than that......
I may have misunderstood. Your LFS is supplying pre-mixed RODI saltwater? For your immediate needs that will work. You may want to look at the overall costs in the long term of buying water from LFS or Spotless Water company (you will need to mix salt with this) or having your own RODI system.
Things to consider in the costs are one time purchase items and then recurring expenditures.
LFS:
One time cost - cost of storage containers (you already purchased) and pump or pumps to circulate the water with mixing salt if necessary.
Recurring costs - cost of petrol round trip to purchase water or if they charge for delivery, cost of RODI pre-mix salt or regular RODI water x liters purchased, and cost of salt if having to mix yourself.
Spotless Water:
One time cost - cost of storage containers (you already purchased), and pump or pumps to circulate the water with mixing salt.
Recurring costs - Cost of water, delivery charge if not included in water charge, salts to mix,
Owning RODI system:
One time costs - RODI system, storage containers (you already purchased) and pump or pumps to circulate the water with mixing salt.
Recurring costs - Cost of water to make RODI water (use worst case factoring of 4:1 ratio for water use), salt to mix, replacement DI media (use 6 months as replacement ratio), replacement filter cartridges every 6 months (carbon block and sediment, 0.5 micron filtration) and RO membrain filter (1 - 2 years depending on water quality).
I may have missed a couple items but this will give you an idea of which is more economical and/or is better for you to work with.
I also see your calculating on a 10% weekly
water change? You may be wanting to consider a 20 - 25% change. As you get your tank operating, things are going to happen and you are going to need more water than you anticipated. Cost are going to be more then you planned. Expect the unexpected. Don't know why but it always happens. The nature of our hobby. The biggest factor in all tanks is water quality and it is the number one item we all use the most, especially when things start to go sideways.
Like you said, you have a steep learning curve, We all did. That's what is fun with the hobby - all the learning, the trials and error, and the victories. The end result is a wonderful tank you are proud of and enjoy.