Each elbow fitting adds to the head loss, which actually reduces the flow rate. You have seven elbows! That might mean a trivial loss of flow rate, but it could also mean a major loss. You would need to measure the flow rate to be sure. Other than that it looks like it should work fine, in spite of not being able to have the CO2 bubbles rise through the water flow. I hope you will do some testing to see how well it works - what bbs it can handle, how much it can drop the pH of the tank water, etc.