how do I make a water cell in my custom table?

I'm not familiar with those mods, but you could probably do this by making a custom tank item, applying a custom NBT number tag that keeps track of how full it is, and then adding a different texture in the 'item properties' tab for each level of fullness. You could then alter the NBT tag whenever you want to change the level of fluid in the tank. (Or just use durability to keep track of fluid level.) I'm not sure if this would be compatible with those mods though.