These are great and I love them had 2 on my previous system, in fact I still have one of them currently set up as a freshwater pond in my fish room. I think I purchased these in 2005 so they last forever barring the random tree limb falling through it while not in use outside. While its 300g its really not large enough for very large fish its only about 50" across which is no where near a 300g 8' tank length. Trust me I had large angels in one it literally took 2 seconds for a fish to go from one side to the other. If aggression broke out there was a constant chase, most fish have a idea in their heads about how much of an area is theirs could be the whole tank depending on size of the tank. I dont know what I was thinking at the time I set mine up, baby sharks are cute but a 2' bamboo shark in one of these looks incredibly dumb, live and learn I guess. I never put a large tang in one (naso) its a bucket list fish for me and if I get one I really want it to be comfortable so unless I get an 8'+ long tank I wont be getting one. The only issue besides being 300g with not that much space for fish to get away from each other is no side viewing so its hard to get a real good look at the fish/base of corals. Top down on a reef is a really nice view though.
I love the rock and over all set up! it looks great! Just saw this and thought I would put my experience out there. Not trying to sound negative or bash I do really love the look of yours!