Circulation question

[warped1]

Sorry to bother you all but I have another question this time it has to do with water circulation. To bring you up to speed… I have a 36gal bow front corner tank. I use a Marineland c-220 canister. Both the intake and return are towards the back corner against the wall They are positioned about 8 inches up from the back corner going towards the front. And directly in the back corner - on the gravel - I have a 10 inch bubble wand powered by a Whisper 40. The intake is simple, a straight tube going down the right side of the tank. The return (on the left side) ends in a diffusion box. It is not a spray bar. It is simply a square cap at the end of the return tube with two slats inside of it to break the current of the returning water. This square can be swiveled to point in any direction. I have it pointing along the left side of the tank in an effort to create a counter clockwise rotation of water current. But with the bulk of the tank size being directly in the center (corner tank) I was wondering if I have enough circulation. Is there a way to test for dead spots? There are no fish in the tank – I’m still cycling. I do have a small internal power filter rated at about 80 gph somewhere in this house I can use to stir things up if need be. But even then I don’t know where to put it because I don’t know if I have dead spots.

[cmor1701d]

The only thing I've seen is cutting some plastic straws to different lengths and attaching them to a piece of wood to be placed at different areas on the substrate. The straws will float and give you and indication of water flow.

I can't post the picture I made, but I'll try again later if you need it.