Where / sponge filter???
In a planted tank, where is the sponge filter best placed? I've a 29 gallon with a fluval U3 and am adding a sponge filter. YouTube shows it at top, bottom and middle. Which place is best? My U3 is back wall center right side. I'd like back or left side, but at what height?
Also, Which end is which on a check valve? The container of check valves has no info.