Best approach for water changes?

[akaps]

Being that you said you are new to this, top off water is done with fresh(as in no salt) water. Preferably made with a ro/di unit or purchased. You could use distilled water from the store if needed.

I do use RO water when I test and salinity is too high, so I guess this counts as a top off?

 

[NC AL]

I don’t top off as I don’t get more than half a gallon, if that, of evaporation between water changes. I think my issue is just doing too big of changes, I’m gonna try doing smaller ones and see how it goes!

Always add in saltwater equal to what you removed. Then top off with fresh water to get back to your set/desired water level in your pump chamber. Even a half a gallon evaporation in a 13.5 (close to 10g) system can be significant.

If you use a smaller freshwater reservoir, you can get away with a cheaper ATO. On my other son's tank (20gallon) is use this as my reservoir and a cheap $40 ATO.

 

[Balthazar]

I do use RO water when I test and salinity is too high, so I guess this counts as a top off?

Ro/di water for top off due to evaporation. Ro/ di water used to make saltwater for water changes.
If the water taken out of the tank during vac or for water changes matches salinity to the-new batch of saltwater there shouldn’t be any difference in salinity. Use the same salinity meter and double check the specific gravity.
If you are not topping off from evaporation before water changes your salinity will rise.