-I looked around on the forums briefly and did not see this suggested; if it has, I apologize-
Nearly a year ago I created a fortress with the simple and humble goal of creating a pit of blood for the glory of our dear lord, Armok. After creating a narrow bridge over a hole several hundred feet where the bottom was jagged spears and broken bones from those that have fallen to spill any future invaders bloods who dared enter my fortress, I found that other than merely dirtying the stone below with nothing but a spilling of their blood, it never pooled like it would water. This made my little dwarf heart sad.
I prayed to Armor, "Armok! Why hath though not leteth me spill the blood of the non believers to create a pool? You are the god of blood, nay"? I then was struck with a fey mood shortly after and only recently completed my task and am now onto this one; suggesting that with enough blood on the surfaces, they can slowly but surely pool.
Lets be honest, we have all wanted to have a pool of blood. They are soooo useful. It serves as a great warning, you can place creatures in it (person favorite would be giant ticks), and I am quite sure they would make great areas for dwarves to hold parties. Plus, you can spot a thirsty vampire in no time with one.
We could all use a pool of blood in our lives and fortresses. Come to think of it, can we make pools of booze? I want to drown my nobles in it. I may be doing an experiment right after this thread to find that out. Then I will see if children can be made even if the parents don't have direct contact with one another.