how long can i leave my return pump off and be fine?

[rydiggs]

my tanks 17.5g drilled with a overflow box. i had to turn the return pump off so i could lower the water to do some silicone work. the tank has a mp10 that is running. how long do u think i can leave my return pump off?

[VW_TDI_02]

The important part is just to have flow in the tank which allows for the oxygenation of the water. As long as you have that, you should be fine. The only thing you would need to worry about would be build up of ammonia/nitrite/nitrate since you now have a smaller water volume which would mean faster build up.