I had a 29g biocube and liked it alot. I got it as my first tank to see if I could actually do saltwater, and liked the fact that it was aio. Depending on your plans, as stated above, hqi model if you plan on the high light corals. I just kept a fowlr in mine, and a few shrooms that came on my live rock, with the pc's. However when I upgraded to a 75g, I got a t5 light and the shrroms are looking alot better. Could be better water quality, could be the lights, not sure. But for what its worth, the cube is a great small tank and you can find them used pretty cheap.