New tank 1st fill

[asylumdown]

Do you plan on ever getting an RO/DI unit? If you don't plan on ever getting one, I personally wouldn't bother. Fill your tank with the water you plan on maintaining it with. Buying pre-made salt water for a 55 gallon is going to get expensive, tedious, and time consuming, so if that's not something you plan on doing on an ongoing basis, don't bother now. A few months after the tank is up and running you'll have replaced it's entire volume probably a couple of times so starting with RO/DI won't matter in the long run.

If you are in the process of getting an RO/DI unit, or you do plan on buying pre-made salt water long term, then by all means, do it for your first fill.

There are some amazing tap water tanks out there, but I will say an RO unit was the best investment I ever made. Sometimes I wonder why my tank is getting it instead of me (we still drink tap)