Buying used tank questions

[Keeks09]

I am buying a 39g tank with 40lbs of live rock she used tap water before but it is an established tank. Should i use some of the water in the tank or just start over?

 

[Radman73]

Any other livestock? There could be all manner of things in the water, hard to say. But yes, in general, I would want to start with all new RODI based salt water.

As for the rock, it may be best to clean it as well depending on the quality of the water that was used. Rocks can bind up phosphate and release it over time causing long term nutrient issues. That's why so many people will cure their rocks first and test for phosphates throughout the process even running lanthanum chloride or GFO to pull the phosphate out.