need help on used 175 gallon tank

[jhawk]

I just bought a 175 tank for a 100$ looking at getting in to saltwater been in to freash for way to long want more of a challenge.The tank was already drilled so im goimg with a sump set up but hears the problem it has 3 holes drilled in the bottom 1 hole is 2inch,2 holes 1 inch all the tanks Ihave seen only have 2 holes in them so what to do with 3rd hole?

 

[ktsdad]

Use the 2" for feeding your sump, obviously.
The 2 1" holes are for 2 return lines. Just split the output of the return pump and feed thru the 1" holes back into the tank.

 

[jhawk]

Thats what i was thinking but was not sure everybody tells me I have to have 2 intakes but I thought the 2inch hole would be for the intake.Nobody in my area has a big tank setup like mine

OK one last thing what is the best way to get the white film off the tank never had to clean a tank this size?