I was about to build a big guardian farm and I wanted to check it with a small one before I waste my time in the big one. So I built a 16X14 room. The water source is at 59th level and the roof is at 60. There are 2 flowing water layer at 58 and 57. The fence gate layer (opened) is at 56th level. The caves below are not lit yet. Not even a single guardian is spawning. I did afk at level 144 but still no use. The room is within the boundaries of the sea temple.
Apart from that I have a skybase exactly above that area which has one cow spawner. Is that a reason for it?