Instant Ocean and Distilled water

[BWV]

Ok.. so I'm trying to be super careful, and have only used boxed water from Petco (Oxymoron?) and distilled water to adjust salinity.
(13.5 Fluval, 4<1" fish, toadstool, GSP, inverts, "liferock", "livesand")

My targets for chemistry are:
Alkalinity 10 dKH
pH 8.2
Calcium 400 ppm
Magnesium 1300 ppm
Specific Gravity 1.024
Temperature 78F
I base these on "the middle ground" from the hundreds of places Im reading...
Been using Seachem Reef advantage Mag(Sulfate) and Calcium(Chloride) and Soda Ash (made from Baking soda 400F for 1 hour).
Salifert test kits.. and my tank chemistry has been spot on.

So... I'm 40 minutes from civilization, and I figured I need another job, I made the decision to mix my own water using instant ocean and distilled water.
Is this a mistake? (the distilled h2O) Should I do RO/DI ... I worry the membrane will dry out, or gum up, as I just wont use a lot of water, and the DI cartridge will just be wasted sitting wet.

At 1.024 after aeration and pump in the heated 78*F tank (10 gal glass) for 36 hours, I got the below parameters.
Alkalinity KH 1.9
pH 8.6
Calcium Ca 320
Magnesium Mg 1020

I tested this 3x ... same results.. then went to my main tank just to make sure i was having a brain cramp.. and my main tank is spot on.

So either this is what I get with IO and distilled h2O, my test kits are bad(and my main tank a mess..which may help explain the other issues I'm having with ich/velvet) or I got bad salt.
I had very little precipitate (maybe 1/8 tsp if that) in 9 gallons of mixed up stuff.
I have been adding calcium, magnesium, and sodium bicarb to adjust (not at the same time, and mixed in distilled h2O) but figured I'd ask in the hopes someone can let me know I'm not mixing a batch of death water.

Thanks for any insight!!

 

[Impala67]

RoDi water is always the best but not always necessary. I’ve used instant ocean and distilled/ rain water for my first tank and everything was perfect, then again I only had softy coral lol

 

[BWV]

So far.. to this solution I have added:
0.75g Sodium carbonate (Soda ash... this was a mistake don't want to raise ph)
150g Magnesium sulfate (Seachem Reef Adv)
7g Calcium (Seachem Reff Adv.. also has small amounts of Mag Chl and Strontium Chl)
8g sodium bicarbonate (Arm and Hammer Baking Soda..instead of more sodium carb)

The water is a little cloudy... but theres no filter, just a pump, so I'm guessing some precipitate in the water.

 

[Impala67]

Also do not use arm and hammer baking soda they produce laundry detergent on the same line, I would buy a food grade rated baking soda and even then just a little I’ve found it doesn’t really help much!

 

[BWV]

RoDi water is always the best but not always necessary. I’ve used instant ocean and distilled/ rain water for my first tank and everything was perfect, then again I only had softy coral lol

Thanks! I was wondering if maybe I was going to be missing minerals and trace elements I'd want later.
As my tank is so small, It's not a huge expense.

I've ordered new/fresh salt to try in a gallon just in case my batch is wrong.
The bag I have is maybe a year old, but not clumped or anything, was kept dry. A friend loaned it to me till I could get to the big town to buy some.

Side note for anyone needing salt - Petco has buy 2 get one free on Instant Ocean, it's on sale, there's a deal if you do recurring delivery, and free shipping on said deal...
I got 3 bags (15lb each, 45 total) shipped to my home for like 17$ total (signed up for recurring delivery)