Aquiring the blue topped castle for my 20gal. tank was perfect, I added blue stones, had 3 oddly shaped recycled blue glass 'chunks', blue LED lite/bubble strip, added my orange, red and blue guppies, and fed an airline into bottom of castle so bubbles come up thru the stacks. Lots of enter/exit holes for my curious algae eaters and snails, as well as guppies to hang out in. It has definitely made the tank a conversation piece. It couldn't be more perfect and especially the price was worth it! We are extremely pleased with it.