How do I find the gauge pressure?

[jle1092]

A rectangular fish tank measuring .75 x .50 m is filled with water to a height of 65 cm. What is the gauge pressure on the bottom of the tank?

So I'm pretty sure I use the equation P=densityxgravityxheight

I know gravity is 9.8, but I'm not sure what height I should use considering it is at the bottom of the tank. Do I use 0? or .65 m? Also, I'm not sure what to do for the density. I don't have the mass of the tank so I can't use mass divided by volume. I know the density of water is 101,300 Pa per 10.6 m of water but I need density to be in kg/m^3 to get my answer in Pa. Can someone help

 

[gneill]

Unless instructed otherwise, take the density of water to be 1000kg/m³, which is 1 g/cm³.

Yes, density changes with depth and temperature and salinity. But it's unlikely to vary much in a few feet of depth in an indoor, temperature regulated fish tank!