Do I really need to buy?

[jazzywashbuckler]

How about this. Why would we need to do a water change when my tanks open top and evaporates and I have to top off?😁😣

[WarDog]

Originally Posted by jazzywashbuckler

How about this. Why would we need to do a water change when my tanks open top and evaporates and I have to top off?😁😣

Because only water evaporates, nothing else.

[reefwars]

Originally Posted by jazzywashbuckler

How about this. Why would we need to do a water change when my tanks open top and evaporates and I have to top off?😁😣

As I mentioned though the main goal is to replenish elements and remove unwanted things like the build up of metals tgat come from mostly foods. When water evaporates and turns into a gas it leaves behind pretty much everything that was bound to it so while water dissappear it removes nothing and replaces nothing