Water Change

[dinotrex]

I've been cycling my tank for about 3 weeks now and I've initially started with saltwater from the lfs. as the water evaporates, should I fill the tank back up with RO/DI water? or keep going with Saltwater?

Same question for water changing, if I'm doing at 25% water change and I'm pulling out the old saltwater, do I fill it back up with RO/DI water? or keep going with Saltwater?

RO/DI means freshwater right? as in Drinking water?

 

[jackdp]

Replacement of evaporated water should be done with RO filtered freshwater. Only the water evaporates, the salts remain. Adding saltwater will increase the salinity in the tank.

For water changes, you are removing a known volume of saltwater from the tank and replacing it with the same volume of water at the same salinity. For example, Siphon out 5 gallons of SW that has salinity of 36ppt and replace with 5 gallons of freshly mixed saltwater that has a salinity of 36ppt and your tanks salinity will not change (assuming perfect measurements, which are really not possible with hobby grade test equipment.) Either way I hope you get the idea HTH