:biggrin: Oh, how I aspire to that type of schedule....but I don't run a skimmer in the 29 cube, so it's 10% every 4-5 days for me.

I weigh mine. Currently using Aquavitro Salinity and 333g is perfect for 2.5 gallons. This gives you 1.025 SG

I just use a digital kitchen scale. In fact I haven't used a refractometer regularly in a looooooong time, although maybe every 10 water changes or so test it just to be sure, and it's always been 100% accurate.

Lol I'm old school I dump in salt until it tests 1.025 on the refractomoter lol

I've found success with a measuring cup using IO. Maybe my measuring cup is off a bit but meh ...

When I add 9x375ml of salt to 26g of RO I get a perfect 1.026 the next evening

Any other volumes I just adjust the #s

I always weigh all the ingredients of my SW and the results are pretty consistent.
I weigh K, Mg and Ca chloride and the salt (I.O.), Lugols solution goes by the drop.