Max Water?

[chenyi]

How much water can I put in my tank? Right now, the water comes through the filter and down this little slide on the back of the tank right into the water. Will that adequately oxygenate the water or does the water have to actually fall down and splash into the water and make bubbles? Or maybe there is some other reason why I shouldn't fill my tank up 100%?

 

[rlederer]

Oxygenation occurs at the water/air interface. The more surface area of water, the more oxygenation. So the more water movement at the surface, the more water is exposed to the air and the more oxygen the water picks up.
But how much oxygen you need depends on the bioload - the number and size and activity of the fish in the tank. One betta in a 5 gallon would do fine with little or no surface movement while a school of zebrafish would need considerable more.

The little waterfall from the filter on the back could be sufficient. If fish hang out near the surface of the water and especially if they take a gulp of air, you probably need more water movement. Otherwise you are probably fine.

 

[flitabout]

Mine has no "waterfall" and some surface agitation most of the gas exchange happens in my HOBs. As long as you have good flow you will have plenty of oxygen in the water.