How Long Can Water Sit?

[ADsnail]

A friend was given a 30g tank with no filter, no lights. He put in sand, decor, plastic plants, and filled it with tap water.

He was just going out to buy a filter, lights, bubbler, heater and thermometer when he was interrupted by a work call--he was emergency on-call for the next week. He works two jobs plus he's been on-call for almost 10 days now; barely enough time for life's basics, much less a trip to the fish store.

He plans to make this a community tank. No one is in there yet. He's kept fish for many years so he knows what to do under normal circumstances. But he's never let water sit motionless like this for weeks. The lid has been off.

The question:
-Should he empty out the water and refill when he finally gets the setup, or will the "old" water be fine?

[Colin_T]

It should be fine as long as no pollutants/ contaminants get into it, and that shouldn't happen in the average house.

The only difference between aerated water and stagnant water is the water movement and amount of oxygen and carbon dioxide in the water. The oxygen level will be higher in aerated water but that's about it.

[ADsnail]

Thank you