I used to have various pumps (Koralias) in addition to my standard wand from my canister in the back of the tank and it is difficult to get them all going in a uniform way. However, about 8 months ago, I tried something that I have come to like much better.
I added a enough of these type of small-diameter spraybars (they connect together to any length) to cover the length of my tank: https://smile.amazon.com/gp/product/...?ie=UTF8&psc=1
. I fixed them to the front of my tank at the very top (each tank will need some creativity in how to attach them) and point them straight down the front glass. My canister is a little too strong with this configuration (causes too much flow), but I found that by rotating the length of the extended bar, I can adjust the flow by finding the correct angle at which the small streams hit the glass. Now, my plants all are in a consistent flow and the tops, in the back, aren't pushed forward as they are with typical flow patterns from pumps/returns placed in the back.
This left the problem of gas exchange, since this bar is pushing straight down. So, I added a small skimmer (https://smile.amazon.com/gp/product/...?ie=UTF8&psc=1
) which does the job. I was able to confirm this by measuring O2 and it rises to ~12ppm (which is quite good), from ~8ppm without the skimmer.