I don't think they provided much sanitation. Not much food, sometimes none, and certainly not enough water.

http://www.historyplace.com/worldhistory/famine/coffin.htm

I figure an average of 350 from this website. I am some ships had more, at least to start with.   This might be new to some people I realize but does anyone know how many people were on these ships? I would guess certainly inthe hundreds...they were practically lying on top of each other..no head room....

I don't believe they would necessarily replace all the ballast..maybe there were 20 tons of Irish and 30 tons of slate or granite or whatever. mg