I was a contractor and code enforcement officer. Your normal construction cannot support the weight. I also have a 300 and had it set up at one time as you are talking. Too much flow in one direction will exhaust your discus. I did that and the discus would not grow. If you put discus they need/require constant water changes or they will not be healthy and they need a low bio-load to thrive. The load you are talking about above is too much for discus if you do not want to do a 50% water change daily. Discus are high maintenance fish. clown loaches are fantastic but they move to suddenly for discus. Discus are jumpy fish and when they are stressed they develop issues like later line disease and wasting. The cardinals are fantastic with discus as are a few of the high temp cories. Remember discus require a minimum of 82 degrees but do really well at 86. There are a few swords that will tolerate the high temps and the standby Anubis family. Bog would is a must with java fern. Remember Discus do not like bright light, it will stress them so there is no need for Co2. the shrimp will be eaten by the discus. My 5-8 inch clowns ignore mine