you can keep one aimed at the surface , and bring the other down closer to the sand bed. without disturbing the sand bed ,
meaning not to create a sand storm !
it has a lot to do with positioning for the best water flow . with what I said you should see a big improvement ,
looking at your tank layout this should solve the flow issue .
helping rid the cayno issue , frequent water changes will also help..
This was my big head ach , I know over kill
I always had a big circulation issues it always drove me nuts , I had lots of dead spots in my 90g mine was because of length and height of the tank along with the positioning of rocks , so I added more power heads ,
6 to be exact . 2 1200's at the surface on either end , 2 900's at the bottom on either end close to the bottom , 2 650's on the back wall on either end facing toward the center front glass mid level , all the extra circulation made a big difference , but how they are positioned keeps the water-flow so it's not over powering was the trick , I agree that's a lot of flow but I don't notice more water movement just way better gas exchange at the surface and less crud resting on the sand and rocks ,