The next few items are really essentials when it comes to reverse osmosis water making.
So lets start with a TDS meter, this handy little device lets us measure the total dissolved solids in water by indication of a number, this number in pure water when using the correct buffers can give you an indication of things like Gh roughly but dont use it for anything else as the machine cant differentiate the different elements, it can only measure. My machines I have bought over the years have always been from the proper manufactures and I suggest you avoid all the cheap knock offs because they no doubt will be unreliable. Here is what I am using now from HM Digital a TDS4
A buffer is required to get the mineral content up in your reverse osmosis water, without it the shrimp would die so its important that you use this.
I use the best buffer on the market called Salty Bee GH+ Premium Check them out on facebook here
This is the best bee shrimp ph lowering substrate I have used to date and I have had a tanks last for roughly 4 years before needing to be replaced, the irony is that once the people that sell this once very cheap bonsai soil caught on to its uses in aquaria the prices shot up to double and treble the original value which is a little sad.
There are of course many places you can buy the soil but just make sure you buy a bag that says HARD BAKED on it, that is very important.
Akadama soil Links