Question on Oxygen levels + filter

[swozzie]

I have an O2 measurement kit that measures in mg/l but I don't know what is good and what is bad. Can anyone help?

Also, I have a well planted tank (using deponit/sliver sand/inert (1.2-2mm) gravel) with an undergravel heater cable that uses convection to move water through the substrate. Presumably my biological filter exists in both the filter and the substrate but which is most effective or most important of the 2 biological filters?

 

[vega]

wat filter u r using?

 

[Guest]

Presumably my biological filter exists in both the filter and the substrate but which is most effective or most important of the 2 biological filters?

Neither, IMO, it's the plants themselves. They are constantly removing nutrients from the water, providing O2 when the lights are on, AND, they also provide tons of surface area for the nitrifiying bacteria to grow on.

Second I would say the substrate, last, filter, no matter what tyep of filter you have. All my opinion, mind you.