I have done 4 or 5 100% changes now (when I moved the tank or tore it down.) if you match your new water to your old waters peramiters then they shouldn't be any problem.. but if all you are doing is switching to RO water and that is the only reason why put your self through all that work.. do a 50% every week for a couple months (sounds like more work to me actualy

) ya go with the 100% and match the Alk, PH, salinity and temp to your old water and go for it.
Steve
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